High Speed Shaking

[Bewolf]

Ok, I am an old boom and zoomer back from the IL2 days. Nothing more satisfying to get rewarded for all that patience in climbing and restraining oneself to go into the furball, specially in aircraft that could be considered bricks otherwise.

However, there are a couple problems with this tactic lately. Preferring the BF110 currently, imho the aircraft with most character in CoD, boom and zooming is an absolute must as direct dogfighting is pure suicide. However, once crossing 500 kph (which actually is close to the max speed of some AC) the aircraft not just shakes, but changes directions and twist around like being caught in a Tornado. Forget about having the time or stability to actually take aim. This also means that 500 kph is the max you can take into zooming again, not a lot really and gone in no time.

The 109 encounters this at around 600 kph.

Was this really this way? If it was, I will shut up, but I have a couple doubts about the nature of shaking encountered. Would be very nice if a more knowledgeable person could shed some light on that.

[Viper2000]

How high were you?

Since the latest patch doesn't fix the high altitude engine problems (which seem to be related to mixture strength), it's possible that you've got engine trouble; obviously this will be worse for a twin than a single. You might also have engine rpm problems. Obviously, anything engine related will cause yaw and roll in a twin.

I don't honestly know what VNE for the 109 and 110 would have been in 1940. However, in IL2 we've got used to pushing many aeroplanes way beyond their published VNE (e.g. I'd regularly exceed 850 km/h IAS+ in the Fw190, when the redline on the ASI in the cockpit was at 750 km/h), just as we also got used to being very casual about airframe g limits or indeed engine handling. So it's possible that VNE is now being enforced more strictly than before.

Doubtless Kurfurst knows the answer to the VNE question.

[Bewolf]

Hey Viper, I think you misunderstood my post. This shaking is not really engine dependent, even with idle thrust and prop pitch to idle this occurs when crossing the 500 kph mark in the 110. You may want to try it yourself to see what it is about. Push your nose down at, let's say, 3000 meters, if you are going full speed even 2000 meter and see what happens once crossing that speed mark. You lose direction control, making it near impossible to line up for shooting. The same happens to other planes long before reaching their maximum speed limit.

[Viper2000]

I tested it.

It's classic directional snaking behaviour. I don't know whether the 110 suffered from it at this speed, but it's not an unreasonable generic high speed (mis)behaviour; lots of aeroplanes from this period suffered it if pushed too fast.

PS - the 110 is a real killer! I got 4 Spitfires in the low level dogfight quick mission. Couldn't find the engine oil temperature though, which was annoying, and the engines died just as I got back to France...

[Bewolf]

Originally Posted by Viper2000

I tested it.

It's classic directional snaking behaviour. I don't know whether the 110 suffered from it at this speed, but it's not an unreasonable generic high speed (mis)behaviour; lots of aeroplanes from this period suffered it if pushed too fast.

PS - the 110 is a real killer! I got 4 Spitfires in the low level dogfight quick mission. Couldn't find the engine oil temperature though, which was annoying, and the engines died just as I got back to France...

Yeah, try that against 4 Spits in Multiplayer
Against everything else she is a killer par excellance. My fav bird here so far, shredders everything appearing in front of her nose, hehe.

Directional snaking, hm? Gotta see what google comes up with here.

Btw, you may want to check the engine nacelles next time you look for instruments in the 110

[Viper2000]

It's certainly no Fw190, but lots of relatively big guns in the nose and reasonable top speed should make it pretty effective against opponents with poor SA (who should be more plentiful now that there's a lot more systems management for people to worry about...).

As for snaking & other aspects of stability & control, try this:

http://history.nasa.gov/monograph12/ch4.htm

[Kurfurst]

Originally Posted by Viper2000

I don't honestly know what VNE for the 109 and 110 would have been in 1940. However, in IL2 we've got used to pushing many aeroplanes way beyond their published VNE (e.g. I'd regularly exceed 850 km/h IAS+ in the Fw190, when the redline on the ASI in the cockpit was at 750 km/h), just as we also got used to being very casual about airframe g limits or indeed engine handling. So it's possible that VNE is now being enforced more strictly than before.

Doubtless Kurfurst knows the answer to the VNE question.

750 kph IAS for 109 (as on all models up to 109K, which increased it to 850), 650 kph IAS on 110.

Different limits were not specified for higher altitudes, ie. it did not decrease with altitude, at least not in the manual (nor did it in 1940 British manuals - although it was only due limited knowledge of Mach effects at the time in both cases, so in reality it was certainly less at altitude). When flutter problems were started to be encountered and people on both sides of the Channel become more aware of it, they tended to decrease VNE at altitude, but left max. VNE near SL the same..

The thing that is odd about the 110 snaking is though that it occurs at low altitudes just as well, at near VNE speeds. If it would be high altitude, I'd understand that its some Mach-related effect.. but its like as if the rudder would be living a life on its own.

Which kinda makes me thing that there are two possibilities:

1. COD has a new hard coded VNE structural dive failure - I have seen similiar on the 109, albeit in much more hairy dives during intentional 'dumb flying', and it sets in earlier because the 110 is limited to 650

2. Engines (props) of the 110 run wildly asyncronized in dive, and this tears the plane apart.

3. Some game controller induced bug with new patch. Curiously, I did have similiar problem with the 2nd beta patch installed, for some reason, my view kept jumping off in the cocpit from time to time without using the HAT switch on the jstick..


What I found annoying though if 1, is the reason, that while no amount of dumb flying (pulling waaay too many Gs with the stick) seem to be able to break the plane, so stupid pilots would not suffer, we may have a rather odd limitation built in by the possible 1. case, which prevents you from even approaching the limits the manufacturers deemed safe yet..!

[Sternjaeger II]

Originally Posted by Kurfurst

750 kph IAS for 109 (as on all models up to 109K, which increased it to 850), 650 kph IAS on 110.

Different limits were not specified for higher altitudes, ie. it did not decrease with altitude, at least not in the manual (nor did it in 1940 British manuals - although it was only due limited knowledge of Mach effects at the time in both cases, so in reality it was certainly less at altitude). When flutter problems were started to be encountered and people on both sides of the Channel become more aware of it, they tended to decrease VNE at altitude, but left max. VNE near SL the same..

The thing that is odd about the 110 snaking is though that it occurs at low altitudes just as well, at near VNE speeds. If it would be high altitude, I'd understand that its some Mach-related effect.. but its like as if the rudder would be living a life on its own.

Which kinda makes me thing that there are two possibilities:

1. COD has a new hard coded VNE structural dive failure - I have seen similiar on the 109, albeit in much more hairy dives during intentional 'dumb flying', and it sets in earlier because the 110 is limited to 650

2. Engines (props) of the 110 run wildly asyncronized in dive, and this tears the plane apart.

3. Some game controller induced bug with new patch. Curiously, I did have similiar problem with the 2nd beta patch installed, for some reason, my view kept jumping off in the cocpit from time to time without using the HAT switch on the jstick..


What I found annoying though if 1, is the reason, that while no amount of dumb flying (pulling waaay too many Gs with the stick) seem to be able to break the plane, so stupid pilots would not suffer, we may have a rather odd limitation built in by the possible 1. case, which prevents you from even approaching the limits the manufacturers deemed safe yet..!

Kurfurst, flutter is an aerodynamic effect, as such is more pronounced where the air is denser, that is to say at low altitude.
Bear in mind that VNEs are not flutter speeds, they're redundant by a certain percentage (Viperpedia might help us here) and do actually vary according to altitude (modern planes have the so called "barbers' pole" that indicated the KIAS VNE according to altitude).

[RAF74_Winger]

Kurfurst, flutter is an aerodynamic effect, as such is more pronounced where the air is denser, that is to say at low altitude.

Wouldn't the damping ratio be increased at lower altitudes with denser air, leading to greater risk of instability/flutter higher up?

I don't know that, just asking the question.

W.

[Sternjaeger II]

Originally Posted by RAF74_Winger

Wouldn't the damping ratio be increased at lower altitudes with denser air, leading to greater risk of instability/flutter higher up?

I don't know that, just asking the question.

W.

Flutter will occur at any altitude, the higher you go, the higher the IAS. Consequently your VNE would increase the higher you go, I am not sure whether they went as far as giving different VNEs according to altitude in those days though..