Stability and Control characteristics of the Early Mark Spitfires

[Al Schlageter]

Originally Posted by Crumpp

What a shame the Air Ministry did not have stability and control standards in place.

They would have realized something was not kosher when the aircraft motion did not align with predicted results.

UGH!!!?

The s/fs had nothing to do with 'stability and control standards'. To bad the Americans didn't have S&CS for the P-51 when they were loosing wings.

[NZtyphoon]

Originally Posted by Al Schlageter

UGH!!!?

The s/fs had nothing to do with 'stability and control standards'. To bad the Americans didn't have S&CS for the P-51 when they were loosing wings.

Just another one of Crumpp's diversions - I'm waiting for his list of Mk Is destroyed through structural failure, along with scans of the relevant pages from Morgan and Shacklady.

[Al Schlageter]

Originally Posted by NZtyphoon

Just another one of Crumpp's diversions - I'm waiting for his list of Mk Is destroyed through structural failure, along with scans of the relevant pages from Morgan and Shacklady.

Not likely to happen, as you, and others, know so well.

[Crumpp]

1567MkI produced/17 structural failures = 92

About the same as the Beechcraft Bonanza.......

No wonder the RAF wanted to solve the issue.






I just thought this one was very interesting.....

[Crumpp]

X4268 went in July 41 to figure out why all the Early Mark Spitfire wings were breaking.

[NZtyphoon]

Originally Posted by Crumpp

1567MkI produced/17 structural failures = 92

About the same as the Beechcraft Bonanza.......

No wonder the RAF wanted to solve the issue.

Thanks for the scans.
Structural failure through what causes? You count dives as structural failure but this is not the same as structural failure through poor longitudinal stability - Henshaw notes that no aircraft could withstand a sudden dive while the aircraft was still trimmed to climb, or with a poorly fitted tailplane fairing shroud, nor do the bare listings say anything about the circumstances.



Spitfire II Pilot's Notes on diving:

DIVING
21. The Maximum permissible diving speed is 450 m.p.h. A.S.I.
Note the following:

(iii) The aeroplane should be trimmed in the dive, i.e. the trimming tab control should be set to give no load on the elevator. This will lessen the possibility of excessive "g" being induced in easing out of the dive particularly if the pilot should ease his hold on the stick owing to "blacking out" or any other reasons. No difficulty in easing out of the dive will be experienced even if the aircraft is trimmed in the dive as the elevator control is comparatively light and recovery from the dive is not resisted by excessive stability in pitch. Elevator tabs may be used, very carefully, as in para. 14.

(Note Henshaw's comments on diving a correctly trimmed Mk V well beyond 450 mph.)

The Pilot's Notes don't warn about longitudinal stability in the dive, and before claiming they do, read the comments properly: They discuss imposing loads during aerobatics, part of which involves a dive. In rough weather it says the pilot could suddenly jerk the stick unless bracing his arm



The NACA report does not mention elevator control or longitudinal stability in the dive.


Ergo, structural failure in dives cannot be attributed to longitudinal instability, there could be all sorts of reasons for such failure to occur, including badly trimmed control surfaces.

So, omitting dive failures we have:

Mk Is less than 1 year old lost through structural failure in flight:

K9977 Ia 191 EA MII FF 16-5-39 602S 18-5-39 lost wing during aerobatics crashed Haddington CE Lothian 30-12-39 Sgt Bailey killed SOC 11-2-40

N3120 Ia 391 EA MIII FF 29-10-39 6MU 3-11-39 266S 20-1-40 broke up in test flight to alt Pilot Gleed thrown out crashed 14.40hrs Littleport Cambs 18-2-40 SOC 22-2-40

X4613 Ia 1233 EA MIII FF 15-10-40 6MU 15-10-40 ? 603S 17-10-40 266S 24-10-40 Lost wing and crashed Gedney Hill Lincs CE 2-3-41 SOC 20-3-41

R6692 Ia 746 EA MIII FF 3-6-40 6MU 5-6-40 609S 7-6-40 Overstressed attacking Ju88 CE 12-8-40 SOC 2-9-40

(R6692 was "overstressed" - without knowing how this occurred this cannot be attributed to poor longitudinal stability.)

Mk Is - older airframes on OTUs lost through structural failure in flight:

R6777 Ia 803 EA MIII FF 21-6-40 8MU 22-6-40 65S 12-7-40 C2 ops 30-7-40 GAL 616S 20-8-40 72S 2-9-40 92S 3-11-40 145S 4-2-41 AFDU 6-3-41 152S 13-3-41 SF H 10-4-41 57OTU 4-8-41 61OTU 3-1-42 Broke up in air and crashed Blackbill Glam FAC3 8-7-42

R6882 Ia 840 EA MIII FF 1-7-40 (CMG) 6MU Brize Norton 28-7-40 cannon wing fitt 7OTU 3-9-40 AFDU Duxford 11-1-41 R-RH 10-2-41 Cv Vb M45 92S 'QJ-N' 9-3-41 609S 30-8-41 Broke up in air and abandoned 2.5m NE of East Stoke Notts FACE 10-1-42 SOC 17-1-42

R7064 Ia 1431 EA MIII FF 5-2-41 9MU 6-2-41 411S 5-7-41 52OTU 23-11-41 struct damaged in spin crashed and hit fence nr Aston Down CE 25-3-42 SOC 3-4-42

X4234 Ia 1031 EA MIII FF 15-8-40 8MU 16-8-40 609S 24-8-40 damaged combat P/O Staples safe 27-9-40 AST 66S 13-10-40 57OTU 1-11-40 FACB 27-6-42 ros wing fail in spin crashed Alsager Cheshire CE 25-9-42

X4854 Ia 1351 EA MIII FF 14-12-40 MU 16-12-42 53OTU into sea nr Dunraven Castle Thought struct fail of stbd wing 2-1-43

Three failures before early 1941 which might be attributed to longitudinal instability, plus 5 older airframes four of which were on OTUs - who knows what stresses and strains these older aircraft went through before ending up in the hands of trainee pilots?

[Al Schlageter]

Originally Posted by NZtyphoon

Ergo, structural failure in dives cannot be attributed to longitudinal instability.

Sure you can NZ if that is what your agenda is. It doesn't matter even if the a/c was exceeding it dive limit speed.

[MiG-3U]

Originally Posted by Crumpp

Again, the failures were notable enough for the RAF to send the plane to be tested to discover why the wings were failing in August of 1940.
...

It was serious enough that X4228 went to Farnborough on 24-8-40 to be used in testing to discover the cause of wing structure failures.

Hm... so it was the X4268 which went to Farnborough for aileron testing Aug 40, the tests for wing failures were July 41.

Interesting interpretation

[Glider]

First of all, credit where its due, Crump has produced the copies with details and for that I thank him.

So we have 4 losses in the front line which are obviously caused by something.
One of these made it home and was probably a bent wing as the aircraft is designated as overstressed. I don't see any other examples so there is no case for saying that this was a significant problem.
The otthers we do not know the details of but the reasons could be many. This is far from proving that the Spit structural limits were easily reached.

What I also find interesting is that none seem to have been lost to spinning which rules that out as a weakness

[NZtyphoon]

Originally Posted by MiG-3U

Hm... so it was the X4268 which went to Farnborough for aileron testing Aug 40, the tests for wing failures were July 41.

Interesting interpretation

This is clearer http://www.spitfires.ukf.net/p014.htm

X4268 Ia 1066 EA MIII FF 24-8-40 AMDP VA 24-8-40 RAE 9-40 aileron trials pilot J Quill. RAE 7-41 flight measurements of wing internal pressure for invest into struct fail of Spit wings. returned VAWD for continuation of trials.
ASTH for flaps mods. CRD AAEE 8-9-41 M45 install. Strengthened flaps tested as air brakes. 18-10-41 trials with thermostatically operated rad shutter ros VA 18-10-41 CRD DeH 23-11-41 39MU 18-2-42 3SGR 10-3-42 CF PRU engine failed wheels up landing nr Weeton Lancs CE 21-4-42 SOC 30-4-42

Opinions of an aerodynamicist:




No mention of longitudinal instability being a problem...
and an accident inspector:





(X4421 Ia 1138 EA MIII FF 12-9-40 8MU 13-9-40 66S 16-9-40 57OTU 21-10-40 steep dive from low cloud violent pull out high speed stall spun wing fail Pilot thrown clear but killed 15.15hrs crashed Northrop Flints 27-3-41 SOC cancel RAE 8-4-41 AST 13-5-41 rebuilt as Va M45 164S 29-4-42 FACE 18-8-42 (Rebuild suspect) )

One of the major causes - aileron instability caused by stretching cable - again no mention of longitudinal instability.