Putting the Pilot's Notes in context:
Also issued along with the Pilot's Notes were Pilot's Notes General A.P. 2095 which explain the limitations in the Pilot's Notes, and the reasons for them: (2nd ed, 1943):
First, the Pilot's Notes were deliberately conservative to ensure that most pilots flew well within the limitations of the airframe thus avoiding too many overstressed, high maintenance aircraft on operational service.

However, the RAF acknowledged that in combat it was up to the pilot to choose what risks needed to be taken; whatever legal status the pilot's notes had in peacetime that legality could be overruled under combat conditions because if pilots were expected to fly by the rules all the time they were easy meat. One reason so many pilots were shot during their first combat was because they hadn't yet learned how to fly their aircraft at or beyond the limits set down in the pilot's notes.

Why spin when you don't have to?

RAF Pilot's Notes for operational single-engine fighters which permit spinning:
Spitfire VII and VIII, IX & XVI, XIV & XIX: Spinning permitted but with a height limit of 10,000 feet.
Typhoon: permitted, without bombs or drop tanks
Tempest V: not permitted until proper tests had been carried out
Mustang III: only when rear fuel tank was empty
Corsair: Spinning not permitted

The simple answer is I don't know how the longitudal instability manifested it's self. As I understand it the BoB weight was specifically fitted because people were breaking spits when coming out of dives. As you say the bob weight didn't resolve the instability because it was an aerodynamic issue. So how could the pilot "make it happen"? Wasn't it happening all the time? I think it was Tim Viggors who recalled writing off a Mk1 spitfire simply by pulling out of a dive, the airframe was so badly bent it was un repairable. He was lucky, the usual result was you said goodbye to your wings.

Can you explain to me how fitting a bob weight would correct an aerodynamic problem? I've never claimed to be an aerodynamics expert and tbh it doesn't really interest me. Despite this, I'm learning quite a bit from this thread.
The reason I ask is that in Morgan and Shacklady there are numerous mentions to the inertia weight, and none of them mention instability, they all however mention pulling out of high speed dives and that it was too easy to break the A/C because of the elevators being so light.

I thought the instability was more of a twitchy thing, as mentioned in the Rechlin trials? Specifically the "suffers from quick changes of trajectory along the vertical axis, coming from high longitudinal thrust momentum, and significantly disturb aiming" bit and the reference to "bad elevator and rudder stability on the target approach". So was the impact of the inertia weight a double edged sword? Ie it resolved the dive problem and softened the elevator problem?

The fitting of bob-weights does not fix the stability issue. It compensates for the stability by increasing control.

It artificially increases the stick force gradiant. This makes the rise in stick forces as we get farther away from our trim point steeper.

In short, it makes the stick heavier so that it takes more effort to move it that 3/4 of an inch.

Right, it is a twitchy airplane under certain conditions and steep turns was one of them.

Yes it was a double edge sword especially for veteran pilots who grew accustom to a two finger airplane.

Nonsense, as they mention the engineering margins are just too tight in aviation. The Operating Limitations are that margin.

They were not "easy meat" by observing the operating limitations. Where do you get this stuff?

The RAF says the exact same thing I told you multiple times...the engineering margins are just too tight in order to even achieve flight. The Operating Limitations are that margin.

Read this a couple of times very carefully to allow it to sink in:

Now, imagine you don't have a reset button and when you skin your knee, it really does hurt.

Yes, by BALANCING that risk.

That means choose your death.....

1. You will die due to enemy action.

2. You might die if you violate the limits. If you do violate the airworthiness of the aircraft, about 85% of the time it will be a factor in your death in an airplane.

It means just that, balance your risk. It does NOT say contact with the enemy is license to violate the airworthiness of the aircraft. Those limitations are based on physical laws that define the airworthy limitations of the design and just like the RAF tells you, a chance exist's you are going to die if you violate them. You want the ability to throw that airworthiness out the window in order in to have some magical performance in your game shape. It does not work that way in reality. The anecdotes from those who survive having to make such a choice of their death are filled with bent airframes and damaged engines for a reason. Just as the RAF warns their pilots. The did it and got lucky.

As for spinning, the RAF clearly warns of the danger of violating manuever limitations in an aircraft and why:

If you still have 1946 installed, you could compare the flying qualities of the Spitfire V against the Spitfire IX. Both are very agile, the V being more unstable, more difficult to fly to the limit and easier to break.

As I understand as weight gained by the time of the Spitfire V's appearance, the airplane tended began to overreact itself in pitch. In short the amount of pitch to stick movement / physical effort on the stick was not linear, and the aiplane 'tightened up' the turn on its own. It wasn't the oscillations ripping apart the plane in the dive, but the fact that pilot could rapidly exceed the safe g-limit of the aircraft due to this. He pulled a bit on the elevator, he pulled 3 g; a bit more which felt natural to be 4 g and he pulled 6 g in fact, and the aircraft accelerated in the turn, increasing the force and he soon found himself either spinning or breaking up the airframe. That's just how a longitudally unstable aircraft reacts, especially as the loadings in the airframe - guns, radios, armor etc. increase - the CoG shift s backwards, making the plane even more unstable. The bob weights progressively increased stick forces, so he was less likely to do that.

At least that's my layman's understanding of it.


Yes that's pretty much why I raised this thread. When I fly different aircraft, I want to feel they react different. I want a Spitfire, a Hurricane, a 109 whatever all handle different, good and bad, I want to learn how to fly them, that's what a sim is all about, right?

Right now they all seem to respond all the same, as if there was a generic handling code which kills the whole point.

Instability/stability characteristics as I understand are about how much the plane moves more (or less) around its axis than its supposed to. Move the stick in one direction, and a positively stable plane stops movement after a while and sets in a stable new course (good for a bomber), a neutral one keeps turning the same, and an unstable one starts turning faster and faster. The latter is good for manouverability, since you can initiate a turn very fast (no delay), but not so great if you want to fly accurate (for aiming), or hold a steady turn and fly near the stall.

As a sidenote, its funny to read German and British test reports on the other guy's plane's control characteristics. In short the Brits write the 109 is too stable, the Jerries write the Spits are too unstable. Go figure, it simply means they had a very different understanding what control characteristics are good for a fighter.

Now stick forces are a different thing, the 109 in pitch required rather high stick forces (20 lbs/G), which is good from the POV it prevents you from whacking the aircraft in dive recovery by pulling to many Gs, at lower speeds the amount of physical effort naturally feels just about right for a given movement, but it is more tiresome for your arms and can even limit you in maximum G (which is kinda the point). In comparison the Spit had very light stick forces in pitch, around 4 lbs /G, which made manouvering a physically easy thing and which you could do without your muscles become tired, but at the same time it presented a danger that if you pulled the stick too far backwards in dive recovery (nothing like high physical resistence there to prevent you) you could easily break the aircraft in two or stall in turns for pulling too much G.

Now in Cod and also in Il2, one of the most annoying thing is that the Spits light elevators are not being modelled. No matter how I tried, I could not break the airframe, even with the stick in maximum deflection. At 4 lbs/G you should be able to do that easily in a dive, by pulling around 13 g. At lower speeds, at this point you are probably stalled and spinning out of control, since no aircraft can pull that much without stalling unless the speed being very very high (stall speed iirc goes up with the square?).

Funny how our dear Jeff first demands the evidence he has seen a great many times himself (the Spitfire pilot's notes), then when is shown that again he changes the subject and begins to say that the Spitfire's (or any other plane's) operational limitations are not really limitations at all, and they should be adhered only at the pilot's will.

Yeah right, the RAF was busy printing out manuals for aircraft and define their flying limitations simply because they had nothing better to do. :D

I think this is slightly unfair. Pilot's who flew 'by the book' generally didn't last very long, on both sides. There are too many stories of people breaking 'planes out of desperation, panic or fear. Lot's of Spitfire and 109 pilot's took thier machines to the limit, and beyond. In fact nearly all the top guys did it.

Pilot's are given notes so that they understand the limits and dangers. There were no referees or people from the ministry flying around enforcing the law...

To simply dismiss this in such a trivial way "limitations are not really limitations at all, and they should be adhered only at the pilot's will." seems petty.

At the end of the day individuals made individual choices. If you returned from a mission with a bent airframe nobody grounded you for it, they just said 'oh he's bent the airframe' and ordered a new one.

@:Crumpp.
All this FAA stuff is a smokescreen. You find me a rule and I'll find you someone who broke it.. What has the FAA got to say about intentionally ramming another aircraft? Or shootng down another aircraft, or bailing out at 500 ft, inverted? Aor what you do when your left foot has just been blown off at the ankle?

That is not correct. Please present some facts to back it up.

It might work for your car but not airplanes. As the RAF tells its pilots, the margin in aviation are very small and the limits represent the point you are risking damage. The limits are just that, limits. They are not bound by feeling, opinion, or heroic fantasy, only physics.

Lot of idiots in the world, of course. In aviation you will find people who think they know better and the rules do not apply to them.

You can break man's laws and get away with it but not the laws of physics.

Notice the RAF does not say the wing will not break even at the upper limit of 4G. Why? Because it can break even at the approved limit because that limit assumes a perfect airframe. The Operating Notes define the limits the aircraft is airworthy.

[QUOTEwing which is intended to withstand 4g should not break until 8g is imposed, but there is increasing risk of strain and failure as g rises above 4. ][/QUOTE]

Absolutely, however some of the limitation were not soft ones. Say the manual may say spinning is not permitted below a said altitude, and it may well be on the safe side. However it wasn't there without a reason. The rules could only be bent to a certain degree, and after that line was left behind, there was no coming back, and no telling of stories.

Mother Nature took care about enforcing it though..

It's not petty, it's realistic. If a plane can only take 12 gs before breaking up, it will at 12.1 g. If its humanly impossible to get it out from spin without having 5-10 000 feet of altitude, you will die in it.

What I find petty is that when some guy damands the same papers he has seen about 2 years ago already (back then the excuse was that it's a 'forgery'), he knows very well about it, then when he is presented with it, he changes to subject and tries argues that it really isn't to be taken so seriously.

The Pilot's notes describe the behaviour of an aircraft accurately. They cannot be just dismissed with that 'oh, its not set in stone'.

Sure not, though I've heard some times the damages were deducted, if it was for careless flying. Combat of course is a different matter, anything goes. As Crumpp said, you take a ris k and choose between certain death and likely death, as cruel as it is.

The question is alway: Which one is which? Is flying within the limits or pressing your luck is more beneficial to your survival in combat? Sometimes its the former sometimes its the latter, and the unlucky ones do not tell stories.

Physics just keep working all the same, those rules cannot be bent.

Just to throw in:

If it was for rules these two men would never have survived:

http://209.157.64.200/focus/f-news/1071076/posts

http://www.dailymail.co.uk/news/arti...-survived.html

BTW there are some similar stories.

Sometimes, for whatever reason, rules can be bent.

Impressive... these guys should try lottery! :)

I'm not arguing the physics. At all. I'm also definitely talking combat.
I'm highlighting the fact that context is important too.

History is important, i've read of at least 2 RAF pilot's intentionally spinning as a way to lose altitude whilst being shot at, and I think at least 1 LW guy. I'd have to check thru piles of books...

I'm sure that plenty of pilot's were killed by their own machines failing well within the limits, after all these were hand built. I'm equally sure some went through the limits and survived. It's being made out in this thread that because the pilot's notes say that xyz will get you killed, you get killed every time. I'm merely pointing out that this is actually xyz will probably get you killed.

I maintain that pilots notes alone are not proof of anything other than recommendations. There are too many variables to simply rely on a set of instructions.

Basically, I agree with you. I don't think the positions that far away from each other either, its just difficult to form thoughts accurately in text on a discussion board. No, nothing is automatic, happening all the time as a certain results if you do something wrong, though the probability is high enough to warrant a warning in the pilot's little book.

OTOH I believe Pilot's instructions report a plane's characteristics faithfully. I guess we can agree on this. ;)

BTW what commonly passes unnoticed: it's the fact that to break up the overload has to be applied for a certain minimum time.

This is a subject that is up to now not well understood by scientists and some research is done on this aspect. But basically if something usually breaks up at Xg it may not so if the time of exposure is very very small.

You will certainly believe like me that 30g is something human bones do not withstand, don't you.

Now you know that acceleration is delta(v)/delta(t) with v being the instantaneous velocity and t time.

Now when I jump from a chair my velocity will be not zero, let's say it is about 2 m/s right before I touch the ground. Now when touching the ground the velocity is reduced to zero, so delta(v) = 2 m/s. This happens basically instantly that's why delta(t)<<1. Which will make the acceleration incredibly high. Delta(t) just needs to be smaller than a millisecond to have a decceleration of 200g. Of course my reflects will absorb the shock but even if I'd just fell to the floor or jumped with stiff legs I would not break them. As much as I can break a plastic spoon easily with my two hands without much effort while it won't break if I threw it with force to the ground.

I for my part as an engineer and scientist am much thrilled and fascinated by this kind of intriguing phenomenon.

Of course this whole thing highly depends on the material as from daily experience I would say that elastic materials can take this ultra short loads much more easily than brittle material.

I guess that the lower the overload the longer the exposure times. So it is not unthinkable that if the overload was only for a little time the plane still might have survived it even if the book told that this never was going to happen.

Also remember that the limits for which the planes were designed were theoretical values based on experimental data on material properties obtained through probe measuring and some hand formula and sort of thump rules. These values also contained a certain margin that was dimension by some regulatory rules based on more thump rules.

No finite element methods back then.

Obviously a pilot would not or only in dispair engage in a manoeuver that he would be certain to break his plane with. Nevertheless his plane might not have broken up against all odds, if he was really lucky.

To be fair to you, you haven't been the main culprit withe the regulations thing.

I feel that there is a strange attitude to using combat reports and pilot's recollections as evidence.
They are the only primary source available on the subject of how these aircraft performed, doing what they were designed, tested and regulated to do. Fly in combat. To ignore them is missing the whole picture. Numbers and physics are equally important. To ignore them is also missing the whole picture.

I read a LW account by one of the top pilots. He said he managed to turn inside a spitfire by flying and managing to maintain such a position that only the slats on one wing were deployed he shot it down, by the same token I've read Brian Lane's account of a 5 minute dogfight with a 109 where he rode they very edge of the stall, behind a 109 who's slats were deployed and who was suffering aileron snatching. He got behind after 2 full 360's, the 109 rolled out and dived away. I believe them both.

[QUOTEImpressive... these guys should try lottery][/QUOTE]

That is exactly it. Impressive and far from normal.

They are not theoretical values for structures. They could teach us a thing or two about subsonic aerodyanmics and piston engine aircraft design. The area's they lacked in were transonic realm, supersonic realm, and stability/control engineering.

Aircraft structure load limits are tested to destruction and are measured data.

Do you know how they tested the structural strength of a wing?

Simple, they suspended it and loaded it up with sandbags until it breaks. Now there are some things you have to do to make it applicable to air loads but that is the basic concept.

Today we use hydraulics.....

http://www.youtube.com/watch?v=Ai2HmvAXcU0

That is not true at all. They are the defined limits of the airworthiness of the design.

Flight situation not noted in Pilot's Notes:
http://http://www.youtube.com/watch?v=XABHcQjCun4

NzTyphoon,

Good humerous story. Does not have anything to do with Operating Notes, though.

Absolutely. Failure points are a range and outliers exist. You can be a lottery winner on either end of that range.

I am sure every poor soul who has looped his aircraft into the ground was hoping to be a lottery winner in the last moments of their life.

Ok. lets have a look to the first Spitfire Mk. II manual:

14. This aeroplane is stable, and rock-steady in flight athigh speed. The controls are not ideal, because it will be found that the aileron control become exceedingly heavy at high speed, while the elevator remains comparatively light and sensitive. Individual aeroplanes vary slightly, but in most cases care is needed in the use of the elevator control at high speed, to avoid sudden increases of load factor, or "g". During a tight turn or loop in bumpy conditions, movements of the pilot's body due to bumps are liable to cause movements of the controls and so large and sudden fluctuations in "g". It is then advisable to press the elbow into the side to steady it.
...
(iii) Stability in pitch.- This aeroplane, though just stable in a dive, tends to be a little unstable in pitch (or foreand-
aft) during turns; as the turn is tightened up so the elevator control tends to become lighter, or, at least, fails to increase in weight to a desirable extent. Therefore, care must be used with this control, especially in rapid manoeuvres. When flying in bumpy conditions at high cruising speed, the pilot's body is bumped severely on the seat, and this is very uncomfortable, even for a short time.

Then to the later Mk II manual revision (downloaded from Zeno's):

10. (i) Stability and control - This aeroplane is stable. With metal covered ailerons the lateral control is much lighter than with the earlier fabric covered ailerons and pilots accustomed to the latter must be careful not to overstress the the wings. Similar care is necessary in the use of the elevators which are light and sensitive.

And then aerodynamically similar Spitfire V manual:

10. GENERAL FLYING (i) Stability: The aircraft is stable about all axes.

Aerodynamics wise there is no difference between these and still early version claims the Mk.II little unstable in pitch during turns just like NACA found out in their tests of the Spitfire VA. However, later revisions of the manuals claim these planes stable. So, what's the difference?

Let's have look to the early Spitfire C.G. (center of gravity) diagram:

http://www.spitfireperformance.com/k...cg-diagram.jpg

Note the CG horizontal position 7.6 inches behind the datum line.

Then the later C.G. diagram for the Spitfire I (this was used for another project but CG related parts are unchanged), it's the same for the II and V:

http://target4today.co.uk/_posted_im...11/CoG_Iab.jpg

Note that without elevator inertia device the CG aft limit is 7.5 inches with the Rotol propeller. The earlier CG position, 7.6 inches, was too far aft without inertia device and the Spitfire VA, tested by NACA, apparently had the same problem (their measurements are not based on datum point but if measured from drawing, the CG during test was certainly close the aft limit if not behind it with the Rotol prop).

The claimed unstability in longitudinal axis was caused by CG being too far aft. Proof of this can be found also from Spitfire XVI manual:

41. General flying
(i) Stability
(a) At light load (no fuel in the rear fuselage tanks, no drop tank) stability around all axes is satisfactory and the aircraft is easy and pleasant to fly.
(b) When the rear fuselage tanks are full there is a very marked reduction in longitudinal stability, the aircraft tightens in turns at all altitudes and, in this condition, is restricted to straight flying, and only gentle manoeuvres; accurate trimming Is not possible and instrument flying should be avoided whenever possible.


PS: The later CG diagram for the Spitfire I also explains well the function of the elevator inertia device. The function and the reasons were the same in the P-51.

Over and out :)

That is not a Spitfire Mk I load plan and is not applicable at all. The NACA was well aware of the CG limits and capable of performing a proper weight and balance.

Read the Pilots Operating Notes as you posted:

Bob-weights......

Thanks MiG - I explained all this in an earlier posting but, as per usual Crumpp and co avoided/ignored/pretended it was irrelevant, with nonsense statements like: and continues to pretend that he knows best about everything...as he has done for years, here and on other forums. *Yawn*

Selective quoting. My favorite sin!

Reading is fundamental.

I noticed that is MIG's first post....

;)

http://www.spitfireperformance.com/k...cg-diagram.jpg

Yeah right, it says "C.G Diagram" in nice big letters at the bottom so people who can read understand it has nothing to do with the centre of gravity of Spitfire Mk Is.

NACA report Measurements of the Flying Characteristics of the Spitfire Va: As per usual Crumpp has fudged what the report actually says:

Crumpp has chosen to completely ignore that NACA's own report states that their calculations might have been in error, nor did NACA know what the cg was with full military load. " The NACA was well aware of the CG limits and capable of performing a proper weight and balance." completely wrong.

;) :rolleyes:

More selective quoting and speculation. :)

Quoting from the tests of the Spitfire I K.9789:

http://www.spitfireperformance.com/k9787-fuel.html

2. Handling and Flying Qualities.

The aeroplane has been flown at the following loadings and positions of gravity:-

Load for Weight (lb.) C.G. Position (inches aft of datum)
Typical service load ---5819---7.7
Extended aft.---5819---8.6
Forward limit---5338---5.8
...
(v) Stability - The aircraft is laterally stable at all speeds except in the immediate vicinity of the stall when it is unstable. The aircraft is directionally stable engine 'OFF' and 'ON' at all speeds, but on the climb this is difficult to assess owing to insufficient rudder bias. Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'. Longitudinal stability records are attached.

Later limits for the Spitfire 1A & 1B without and with the elevator inertia device (bob weigh):

http://target4today.co.uk/_posted_im...11/CoG_Iab.jpg

3 With original standard elevator
Elevator inertia device---NIL---3.5 lb.---6.5 lb.
with De Havilland propellers--- 7.9 in.---8.2 in.---8.6 in.
with Rotol propellers---7.5 in.---7.8 in.---8.2 in.

With the Rotol propeller (as was in the Spitfire II and NACA tested Spitfire VA), the typical service load CG of the K.9787 was beyond the later limits without the inertia device (7.7 in. vs. 7.5 in limit). The extended aft CG of the K.9787, 8.6 in. aft the datum point, was clearly beyond the later limit, 8.2 in. even with the heavier 6.5 lb. weigh in the inertia device (with Rotol propeller).

RAE on the NACA stability testing posted by lane:

http://forum.1cpublishing.eu/showpos...&postcount=175

2.2. Stability and control at medium and low speeds. This was covered admirably, with the exception of static longitudinal stability. Trim at two C.G. positions were not done, so that the neutral points remained undetermined.

NACA did not test stability at different CG positions and, as NZtyphoon noted, they had no documentation about the correct CG limits nor accurate drawings.

Over and out :)

All this writing, or better copy 'n pasting, doesn't change the fact that the stick forces and stick travel for the elevator control in the early marks of the spitfire were too low and that has been changed in the later marks with the "BoB-weights".

If the low forces in connection with the small travel weren't regarded as dangerous, no change would have been necessary!

not true, it was merely improved, not changed because it was dangerous, was everything that changed with the 109 do so because it was dangerous? I keep hearing how fantastic the leading edge slats were and then they were removed.........

Now that will be really, really hard to proof, All Bf109 / Me109 had and still have the slats!

And the rest of your opinion is grasping for straws, imo.

IMO all the theories on the spitfire so far are the same.

The reason bob-weights were adopted was because several Spitfire Vs had been destroyed through poor loading at squadron level; this has been explained by Supermarine's Chief Test pilot Jeffrey Quill, although some Spitfirephobes consider him to be so totally biased he's incapable of telling the truth :rolleyes: Of course we have to believe these "experts' such as Crumpp or Barbi, and not Quill, who was the chief propagandist of the Spitfire: :grin:

To say that they were adopted because of inherent design problems with the Spitfire Is and II is wrong; they were used on the Spitfire III because it had developed cg problems and adopted in Spitfire Vs because of poor loading and increased equipment.

Some pilots had the slats were wired shut, but that was the exception not the rule.

Sorry NZTyphoon, but to say that the bobweights were introduced because of the "poor loading ad squadron level" sounds absolutely unconvincing to me.

The bobweights were used to reduce the ease of motion when actuating the elevators, reducing this way the possibility to inadvertently overstress the airframe, regardless of the flightsituation (spin, overspeed or else).

It might sound unconvincing to you but its the truth - unless, like some others on this forum, you believe that you are more of an expert on the matter than Jeffrey Quill.

http://target4today.co.uk/_posted_im...11/CoG_Iab.jpg

The inertia device (bob weighs in other words) was not needed if the CG was forward enough and the later marks, (VIII, IX...) did not have the device because the heavier engine moved the CG forward, 4-5 in. aft of datum point, except rare case of rear fuselage tank.

It can be said that the original CG limits were too aft with Rotol propeller and longitudal stability suffered, hence warnings in the early version of the Spitfire II manual. However, warnings were removed once the limits were revised.

Over and out :)

It is always possible to exceed safe margins through improper loading, but in case of the Spitfire, this margin was small by design; and if it is impossible to maintain safe limits in everyday service, it is a design problem. Saying it was just improper loading, or saying it was just faulty design for that matter, imho only is half the truth.

Yes I just realised I meant disabled instead of 'removed', also it was an idea theorised by the americans on how the 109 might be improved after tests on captured aircraft.

In some degree I agree, the same revised loading table also has limits for the modified elevators:

1. With modified horn balance elevator (Spitfire modification No. 789): - 9.0 in. aft of datum point.
2. With Westland convex elevator (Spitfire modification No. 743) - 8.2 in. aft of datum point.
Note: - 1. & 2.apply to all propellers no elevator inertia device should be fitted.

So there indeed was design changes to solve the problem but I won't call that as a design problem because the loading needs grew over the original specification.

Over and out :)

I think you're right about the narrow cg margin, not forgetting that when the Spitfire was designed in 1935-36 features like CS propellers, armour plate, armoured windscreen, IFF - even apparently small details such as extra ducting for gun heating equipment, shrouding for the gun bays etc - were three to four years into the future. Compare the equipment loaded into a pre-war Spitfire I with that loaded into a 1942 Mk V and the margin for error must have been relatively small.

Does anyone have any idea of how the Spitfire cg margins compare with (say) the P-51?

The text you quoted, nztyphoon, says that the Spit1a b and the spit 2 had no stability problems and then continues with the cog problems of the spit 5.

There is nothing wrong with this text, but is it really applicable to this topic?

If the spit2 didn't had have stability problems, as you quoted, why were bobweights mounted?

Bob-weights have absolutely nothing to do with CG limits. The stabilty margin will shift with CG limits and the early mark Spitfire did have stable load conditions.

However all of that is completely irrelevant. CG shirts from consumption of consumables like oil and avgas. The NACA was well aware of all these characteristics and could do weight and balance.

The solution for the unacceptable and dangerous longitudinal instability of the Spitfire was bob-weights. These were added not because the NACA made a mistake in some half baked theory on weight and balance calculations. They were added by the RAE to correct a serious stability and control issue with the design.

http://img832.imageshack.us/img832/2...htsresults.jpg

Do you have a source showing thes unnacceptable and 'dangerous' in particular used to describe the Spitfire?

NACA......

Operating Notes....

RAE.....

Air Ministry....

Take your pick.

So you say the Spitfires own operating notes say it is an unnaceptable and dangerous aircraft?.......verbatim?.......post some scans.

"Dangerous" I don't believe appears in the NACA Spitfire document that is imo an embellishment. The term unacceptable also needs to be qualified ... it was unacceptable to the criteria NACA was using.

No that is in the Operating Notes....

Yes, the only defined standards in the world at the time besides the German's. Post-war, the RAE adopted the exact same standards as the NACA.

So, we can say in 1940, the RAE had no standards, they just knew they had a dangerous airplane so they warn the pilot often.

In 1946, the early mark Spitfires would have been labeled as "unacceptable" by the RAE but since they had to have bob-weights, there was no need.

You won't find a Spitfire flying today without bob-weights.

They warned the pilot often in one set of Pilot's Notes and nowhere do they say the Spitfire was dangerous. They talk about the onset of blackout during high G manoeuvers but that's it.

Meaningless, purely hypothetical, therefore irrelevant - the early Spitfires did not need bob-weights in the elevator circuit they came later on the Mk Vs and were superseded by the larger, reshaped elevator mass balances.

How about a little proof?

Just for interest this story of X4276 describes what a young, trainee Sergeant thought about the dangerous Spitfire:

Be careful as that "doddle to fly" comment is assuming a fit flight trained RAF pilot moving to the type from something "horrible to fly" like a Gloster Gladiator.

Its very easy to assume doddle to fly means an unfit non-pilot could probably jump in and take it safely for a spin after a few hours training but that is simply not true. Otherwise we would train on Spitfires not Cessna's.

Thread drift but the Gladiator was actually renown for being an absolute delight to fly too :)

For a beginner or for a experienced pilot??

I bet the later.

The same with the spitfire elevator lightness, it probably was a delight for a experienced pilot to fly with "two fingers", but very exciting for the still a bit "ham-handed" newbie who had to rely on the pilots notes and basic training instead of experience..

There seems to be a huge underestimation as to the training that takes place before a pilots is given a front line aircraft.

To say but very exciting for the still a bit "ham-handed" newbie who had to rely on the pilots notes and basic training instead of experience is way off the mark. Trainees of all airforces had some form of primary training, advanced training and conversion training.

Gladiators were used in the RAF as part of the conversion training and the best advanced trainers are 'twitchy', Germany used He 51's and no doubt other airforces used similar machines. Early versions of the Hurricane and Me109 were used in conversion training and one of the major problems the RAF had were that there were no earlier versions of the SPit so they were in short supply, hence you often hear that new pilots only had 8 hours on spits when going to the front line. To believe that they relied on basic training and pilots notes is far from the truth.

Also the idea that because pilots of an aircraft were banned from intentional spinning meant that the plane was a danger and could break up is also rubbish. The early Spit 1 pilots notes say that intentional spinning is banned also go on to say that its easy to recover from an accidental spin as long as you allow enough height and ensure your speed is 150 mph. I am sure Crumpp who has extensive spinning experience will agree that the two golden rules are a) make sure you have sufficient height, b) Get your speed up to a safe level

Why did they make this distinction for the first Spits I don't know and no one else does here. There are loads of theories based on various assumptions, wishfull tinking and misapplication of current theory based modern rules designed for civilian use so I will add another one to the pile.

The first Spit pilots in the front line often only had very low hours on type and front line units didn't have Trained Instructors o they wanted to limit the risk. Later on training on the SPits was more rigourous and they lighted up the rules.

I find it somehow confusing that you first try to contradict me and then say practically the same with different words as your opinion.

Puzzles over puzzles.

I was under the impression that your comment about but very exciting for the still a bit "ham-handed" newbie who had to rely on the pilots notes and basic training instead of experience was to do with the Gladiator as well as the Spitfire, my mistake.

Wow....

:grin:

Everything is covered in the Operating Notes. The RAE and the NACA were in agreement about the longitudinal stability and control.

Granted, the RAE had no standards outside of opinion so they did not know they were in agreement with the NACA conclusions at the time. Interesting paradox regarding stability and control engineering history.

Everything the NACA concludes is listed right there in the Operating Notes published by the Air Ministry as a caution for Operating the aircraft.

But nothing about the aircraft 'breaking up'

Maybe, but flipping through the records of the RAF prewar Gladiator Squadrons there are an awful lot of "abandoned in spins" , "overshot/undershot runways" and numerous collisions with other aircraft (generally at night) along with one collision with a house in Sussex (admittedly in fog), one with powerlines, one hedge and several with trees.

The squadrons were losing several pilots a year in Gladiators and this was in peace time.

Also note that RAF investigations showed that pilots trained on Gladiators made better Spitfire pilots than those trained in more mundane training aircraft.

You seem to have missed the rest of that posting:-

The early Spit 1 pilots notes say that intentional spinning is banned also go on to say that its easy to recover from an accidental spin as long as you allow enough height and ensure your speed is 150 mph. I am sure Crumpp who has extensive spinning experience will agree that the two golden rules are a) make sure you have sufficient height, b) Get your speed up to a safe level

With your experience do you agree that the two golden rules are as stated?

If so, then what is dangerous in the pilots notes about spinning?

This might be of interest

thought I remembered reading an interview on this subject many years ago- and finally found it in a yellowed copy of Alfred Price's 'Spifire At War' (published 1974). It's germane to this discussion (as my teacher used to say) because the person being interviewed is none other than Mr Eric Newton who spent the war with the Air Accident Investigation Branch. He was still employed by them as an investigator in 1974- the time of the interview- so presumably still had the facts at his fingertips. This body was, and is, independent of the RAF.

Mr Newton was called in to investigate Spitfire crashes which could not be immediately attributed to pilot error (the same crashes which are detailed in Morgan and Shacklady). He says:

"Out of a total of 121 serious or major accidents to Spifires reported to us between the begining of 1941 and the end of the war, 68 involved structural failure in the air. Initially the most common reason for such failures, with 22 instances in 1941 and 1942, was aileron instability. The symptoms were not at all clear cut: the aircraft were usually diving at high speed when they simply fell to pieces. Only after one of the pilots had survived this traumatic experience and parachuted successfully were we able to find the cause. During his dive he saw both of his ailerons suddenly flip up, producing an extremely violent pitch- up which caused the wing to fail and the aircraft to break up. In collaboration with RAE we did a lot of tests and found that aileron up- float was made possible by stretch in the control cables; in those days tensioning was a hit or miss affair with no compensation for temperature. On our recommendation the RAF introduced a tensometer which ensured accurate tensioning of the controls; this, and the simultaneous introduction of metal surfaced ailerons ('42/'43), cured almost all the cases of aileron instability in the Spitfire.

The next most serious cause of structural failure in the Spitfire was pilots overstressing the airframe. She was extremely responsive on the controls and one must remember that in those days there was no accelerometer to tell the pilot how close he was to the limit. So it was not difficult to exceed the aircraft's 10G ultimate stress factor (what was the 109's?-) during combat or when pulling out from a high speed dive; during the war we were able to put down 46 major accidents to this cause, though undoubtedly there were many other occasions when it happened and we did not see the wreckage. Incidentally, if there was a structural failure in the Spitfire it was almost inevitably the wing that went; the fuselage was far less likely to fail first (the same for most low wing monoplane fighters?-except the Typhoon?- Berkshire).

I once asked a very senior RAF officer why the accelerometer- technically a simple instrument- was not introduced during the war. He replied that he was sure it would have an adverse effect on the fighting spirit of the pilots (same was said re the parachute in WW1!- Berkshire).

Whether that would have been so I cannot say. But I do know that when they finally introduced the accelerometer into service in the Hunter in 1954, and began educating the pilots on structural limitations and the dangers of overstressing, accidents to this cause virtually ceased.

After structural failure the next largest category of accidents proved on investigation to have followed loss of control by the pilot (36 cases). Of these 20 occured in cloud and could be put down to pilot error; one must remember that in the rush to get pilots operational instrument training was not up to peacetime standards. A further 13 accidents were shown to have been caused by oxygen starvation; the oxygen system had been used incorrectly with the result that the pilot had passed out and the aircraft had crashed. As a result of our investigations the system was modified to make it easier to operate.

The remaining 3 accidents in the loss of control category were initiated by the pilot pulling excessive G and blacking himself out.

Engine failures and fires contributed a further 17 accidents, and the remainder could be put down under the 'miscellaneous' heading.

As I have mentioned we investigated a total of 121 Spitfire accidents during the war. The causes did not always fit simply into neat categories mentioned above. For example, a pilot might lose control in cloud and his aircraft then broke up in the ensuing dive due to aileron instability- in that case the accident would have been listed under two categories. There were one or two accidents caused by the light- weight plastic bucket seats fitted to some batches of Spitfires. The trouble was they were not strong enough and if there was a heavy pilot who pulled a bit of G they tended to collapse- on to the elevator control runs which ran underneath. We soon had that type of seat replaced.

In the nature of my work I tend to concentrate on an aircraft's failings and ignore its good points; but how safe was the Spitfire? I think the figures speak for themselves; a total of more than 22,000 were built, and we were called in on only 130 occasions- and in not all of those was the Spitfire at fault. If one considers that she was not a simple trainer built for ease of handling, there can be no doubt that the Spifire was a remarkably safe little aircraft."

To summarise:
There were 121 Spitfire crash investigations between 1941 and May 1945 involving serious structural failure:
22 aileron instability
46 pilot overstressed airframe
20 pilot error in cloud
13 misuse of oxygen system- pilot error
3 pilot blacked out
17 engine failure/fire

Breaking up in a spin doesn't even get a mention,

I should add that this is copied but I cannot find who the original poster was, but the comments are of interest. If anyone should know please let me know as they deserve any credit

Yes and just as the Operating Notes warn, it is the recovery that is dangerous to the airframe.

Understand?

46 pilots died from it.

Loss of control is not very well defined, Glider. A spin accident though IS a loss of control accident.
http://www.faa.gov/news/safety_brief...r2012Pilot.pdf

Statistically, a very high percentage of those loss of control accidents is a spin.

not from spin recovery

It is the second highest catagory of accidents in your investigation. You really did not know that as a pilot?

Sure they did, not all of them of course but if you get the details a significant number of those Loss of Control accidents resulted in overstressing the airframe from recovery.

Just as the Operating Notes warn.......

all aircraft operating notes warn about overstressing, Spit notes 'do not' say spin recovery 'causes' overstressing.

Not really bongodriver.

You would have a very hard time overstressing the Bf-109 for example. Especially if you followed the later instructions and did not trim the aircraft during the dive.

It was designed that way through good stability and control engineering.

An example chosen entirely at random perhaps?

The first that comes to mind is that the stick forces in the 109 were too high to pull out of a high speed dive without using trim.

Too high or even high stick forces make a involuntary overstressing really tough work.

the airframe will get stressed enough when it lawn darts.....

Aileron instability as well. Interesting.

Not disputed by me (someone else may know different). My point was that the Bf 109 was one type of aircraft, which may have been unusual, would you care to name, say, five others that were also unable to be overcontrolled?

just out of curiosity, is there a NACA test on the 109E?

Sorry, there is only one other where i know it for shure, the Me323 "Gigant" where sometimes in rough conditions one pilot alone didn't have enough power to steer it at all. :D

But "unable " to be overcontrolled stretches the point a bit far, i think.

Every plane with "normal" stick forces and travel was less likely to be overcontrolled with the probability therefore reciprocal related to the stick forces.

Nowhere does it say that recovery is dangerous to the airframe unless you exceed 10G. However if you exceed 10G in any aircraft then or now your chances of making it back in one piece is very limited. I have seen an F4 which pulled 12G and made it back, but it never flew again. We used it for training purposes.

Yep, do you?



You need to read the postings before making comments. Just to remind you what it says:-
The next most serious cause of structural failure in the Spitfire was pilots overstressing the airframe. She was extremely responsive on the controls and one must remember that in those days there was no accelerometer to tell the pilot how close he was to the limit. So it was not difficult to exceed the aircraft's 10G ultimate stress factor (what was the 109's?-) during combat or when pulling out from a high speed dive; during the war we were able to put down 46 major accidents to this cause, though undoubtedly there were many other occasions when it happened and we did not see the wreckage
Where does it say in a spin?
With your experience in spinning can you tell me how you can pull 10g in a spin, in an aircraft the Pilots Notes say is easy to recover from as long as you have height and make a safe speed?

A spin accident is a type of loss of control, all loss of control accidents are not Spin accidents.

I urge you to read these papers before you post comments, It summerises that of the fatal accidents 41% ended in a stall/spin but the split between these isn't given and I am sure you agree that there is a world of difference between the two. Its also worth remembering that the key word is ended in a spin, the reason for the accident could be something else.

Another factor is that these are mainly pilots who haven't been trained in spinning. Instruction in spinning isn't part of the requirements for a PPL in the UK and I believe its the same in the USA. Fighter pilots would have been trained in spinning

Spinning is a requirement in the UK for Glider Pilots and you have to pass a number of spinning scenarios before you are allowed to even solo. The final one is to enter a full spin at 1,000 ft and recover before you lose 300ft. As an ex instructor I promise you this isn't easy for some people to learn.

As far as I know a 109E was tested by NACA but the report doesn't seem to be available in their archives http://ntrs.nasa.gov/search.jsp - some further digging may be required.

Ouch, we could have an interesting debate on that but lets keep it to one topic at a time

Does anybody have further details of this Spitfire aileron instability problem the aircraft seem to have been suffering from?

You can pull 10G on the z axis anytime you are over 218mph IAS in a Spitfire.

You need to be "well over" 150mph and at 150 mph you are only 68 mph away from the ability to destroy the airframe on a single axis load. That is not very far away.

Problem with spin recovery is you are not on a single axis load as it requires rudder input to recover.

I can see why so many airframes broke up on recovery.

How many? sources please.

I have a report on it somewhere, see if I can dig it up.

On what? Pilot stories and opinions?

Of course they are going to be cussing, scared, and pissed after yanking on that stick with both hands to get 80-90lbs of stick force required at Vne. They will be alive and complaining, LOL.

;)

sounds to me if they didn't start with enough altitude then they won't be alive to complain, give me light elevators any day over ones that can't pull me out of a dive.

If any aircraft exceeds its max stress load then the chances are that its going to break up, it isn't specific to a Spit. I think I am right is saying that an F16 is stressed to plus 8G, so 10G in a Spit doesn't sound too bad.

I also ask how many broke up on recovery or are you saying a stall is the same as a spin?

:rolleyes::rolleyes::rolleyes::rolleyes::rolleyes: :rolleyes::rolleyes::rolleyes::rolleyes::rolleyes: :rolleyes::rolleyes:

The absolute magnitude of the load is completely irrelevant when you're comparing a modern jet fighter with a spitfire. What a ridiculous comparison.

What matters is the magnitude of the load as a percentage of the maximum load. Pulling 8G means very little if your airframe is designed to withstand 14G. But if it's only designed for 9G then you better be cautious.

Thanks. I knew about the pitch characteristics, but the ailerons are somewhat new. I suppose it has something to do the Frise ailerons? Balancing seem to be an issue with these.

Let me rephrase it for you. I believed incorrectly that the airframe for an F16's was stressed to a max of 8G so it was my mistake. The normal max for an F16 is 9G due to pilot strain. However it doesn't alter the fact that 10G for a WW2 aircraft is pretty good

Are you any closer to saying how many broke up in a spin?

Some random light relief to break up the technical stuff ...

http://www.youtube.com/watch?v=_u4Md_aXVJE

False comparison, the weakest point of the Jet fighters is the human physiology and the Jet engine. These two causes the restrictions, not the aircraft's structure.

Frise ailerons are a pain to balance and rig. The FW-190 was plagued with adjustment issues too.

http://img824.imageshack.us/img824/7571/highspeed1v.jpg

http://img812.imageshack.us/img812/7978/highspeed2.jpg

Yep, fabric covered ailerons which, as Quill explained, had to be individually trimmed, using lengths of cord then matched as pairs to each airframe. It would be interesting to see whether the same problems continued with the much stiffer metal covered ailerons.

At the risk of being OT:

F-16 accident database/

F-16 crashes up; attributed to human error.

Although the F-15 did have a structural weakness:

2007 F-15 breakup

We hve been writing this in evry sense since the sim is out: the Spit does not bleed E in turns.
It can loop ard anything without rest like a toy loop around the chest of a young girl dancing the Hula hoop.

Frankly if with such a good eye you are a newbie, I want to see tons like you flooding the server and sweep out all those rusty IL2 vets tht stand to their old Oleg world (I am also refering to the other FM thread like the G cut out, the ammo etc... etc..)

Hi. I do not know what to look here :), but some of our squadmates flying in the HuAF. VO101_TB, who Gripen pilot tell a story 1-2 years ago. One of his RL squadmate was an idiot, and pull 12G in the Gripen (The stick have a security knob (10G limit), which stuck the stick. The guy continued to pull). The plane landed without problems, but the aircraft had been sent back to Sweden for inspection. He said, the great G force may bend the engine, but the structure has to withstand smoothly.
Maybe the older F-16 type structure is weaker, so I do not know. Of course, fuel load and weapons load affects the G tolerance. This is clear.

Amen my friend!

The irony is that the same claim about no energy loose of Spitfires were frequently stated in the good old Oleg world ;)

all the time, lol!

Thank you for the compliment! I've Flown a lot of Rise Of Flight since it came out, but I'm still learning on this sim. I figured I was kinda expecting the 2 aircraft to perform like the Se5a (ME-109) and Sopwith Camel (Spitfire). The Se5a is faster and climbs better, but does not turn as well sustained but can, in exchange for much energy pull lead for a short time. The Camel on the other hand can make very sharp turns...but has poorly balanced controls in the case of a sensitive elevator like the spit. One can over turn the aircraft. Flying her with a light touch the Camel can dance around anybody...but ham hands McGuee will just stall and spin out of the sky. These flight characteristics are a bit exaggerated since the Se5a is much faster than the camel and the Camel in turn Turns way, way better where as the ME-109 and spit are a bit closer. However, I Found this to be nowhere near the case with the Spit. Sure, the ME-109 Acts like my classic BNZ fighters...the Spad and Se5a...but the Spit is nothing like the camel because it seems to un-historically have no extreme sensitivity to the controls.

It's interesting to hear that the Idea of the Spitfire not losing E has been around since the original IL2. Is it possible certain details of the FM have been kept over? It could be interesting for the devs to see how much code was held over from older games and if that is causing out problem now.

I hate the expression, "bleeding energy"....

There is not such thing in aircraft performance. There is only sustainable performance and instantenous performance.

If it the performance is sustainable then the aircraft can achieve that performance until it runs out of fuel.

There is not an aircraft in existance that can sustain instantenous performance so it is just silly to talk about it as "bleeding energy". In fact, the generally speaking aircraft with the higher braking forces will win the instantenous turn competition. All aircraft at the same angle of bank and velocity will make the same turn.

"I hate the expression, "bleeding energy"....

There is not such thing in aircraft performance. There is only sustainable performance and instantaneous performance."

So when a manoeuver diagrams have values of negative Specific excess power (Ps) and these are used to compare sustained turn performance and energy bleed rates between 2 aircraft what do you call it ?

The worlds fighter pilots use the term "Energy Bleed' everyday. ...... but I guess they are all misguided dealing with the real world rather than theoretical commentary.