Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: nrshida on October 10, 2013, 10:45:08 AM
-
I've been reading a little bit about the Spitfire to see if I could find any real life accounts which match the handling characteristics of our in game version. Specifically I was looking for info regarding the virtually unrecoverable flat spin and inverted flat spin AH's Mark I enters so readily. I can find no mention (although my Spitfire library is hardly extensive). The aeroplane is consistently referred to as docile, pleasant to handle and forgiving. Surely a far cry from what we have.
I then read up on spins and contributing factors and formed a theory / question:
Does AH's Spitfire Mark I have its centre of gravity too far aft?
-
I'd say the tail "lets go" too soon, but I'm no Spitfire pilot.
-
I don't fly the Mk1 much but it never struck me as nasty as you make out! - Just horrible peashooters for guns!
An interesting article on it here http://www.spitfireperformance.com/spit1vrs109e.html (http://www.spitfireperformance.com/spit1vrs109e.html)
Perhaps more relevant http://www.spitfireperformance.com/k9793.html (http://www.spitfireperformance.com/k9793.html) With spins taking typically 3/4 turn to recover from. I get the impression that the flat spins, should you be so unfortunate to enter one are not representative of the mark. The nose should drop leaving you in an attitude that can be recovered from. Otherwise The handling is very much forgiving.
-
The nose should drop leaving you in an attitude that can be recovered from.
Exactly. The nose not dropping automatically suggests too much rearward CofG does it not?
-
I find it hardly surprising. "Elliptic" leading edge which would lose all its lift along the span in stalls and very small rudder which was increased in size all the time when the aircraft was getting bigger engines.
I recall that even Hurricane had such a bad stall that there was a small fillet that was added under the tail during the prototype stage to help in regaining control in stalls -and Spitty has a lot smaller rudder. Why Hurricane, because they both have big wings and low wingloading.
"The aeroplane is consistently referred to as docile, pleasant to handle and forgiving."
Well, I find AH Spitty to be exactly that. Or do you expect that a high lift wing to handle anything if you hamfist the overly sensitive elevator full back? I'm sure it was pretty pleasant and forgiving in normal flight states but was a beast when pushed over the limit.
This test report may give a clue:
http://www.spitfireperformance.com/Spitfire_IX_ML-186_Handling.pdf
With a bit too much weight in rear tank the handling was considered as dangerous. This leads me to think that even the IX was prone to shift its CoL forward in spin leaving the CoG to rotate the plane if stalled and spun. This supports the view that Spitty needed immediate correction when entering an accelerated stall or the stall, and more like the spin, would quickly develop dangerous.
-C+
-
Exactly. The nose not dropping automatically suggests too much rearward CofG does it not?
In isolation I would agree, but this would also have a negative impact on handling generally, which is not the case. Perhaps the centre of pressure is not moving as one might expect.
-
I find it hardly surprising. "Elliptic" leading edge which would lose all its lift along the span in stalls and very small rudder which was increased in size all the time when the aircraft was getting bigger engines.
The Spitfire wing has washout and doesn't depart in that way. The root departs first and gives a clear buffet long long before the tips go. A larger rudder is needed with added torque and thrust, you are implying it was a design flaw.
http://www.spitfireperformance.com/Spitfire_IX_ML-186_Handling.pdf
With a bit too much weight in rear tank the handling was considered as dangerous. This leads me to think that even the IX was prone to shift its CoL forward in spin leaving the CoG to rotate the plane if stalled and spun. This supports the view that Spitty needed immediate correction when entering an accelerated stall or the stall, and more like the spin, would quickly develop dangerous.
I think your reasoning is faulty. The significant change in this Mark IX was to it's CofG by way of the rear tank. Your view is not supported by the flight tests of normal (no rear tank) Spitfires I have read where they had to be held in a spin, letting go of the stick would allow the aircraft to correct itself.
The paper is useful but not in the sense you mean because I actually think it has added weight to this hypothesis. The non-standard rear tank moves the CofG rearward as it is filled and this Mark IX is demonstrating longitudinal instability during flight testing.
Or do you expect that a high lift wing to handle anything if you hamfist the overly sensitive elevator full back?
I expect the AH model to behave as described in real life which I contend it doesn't.
Look at the comments in your paper about the aircraft tightening up in turns. If the CofG is much farther to the rear than designed for then the tail is dropping harder in the turn and this causes an autonomous tightening of the turn. This makes it much harder to ride the turn and would make the aircraft more difficult to handle and more likely to depart unexpectedly. Then you are in a world of pain once departed because your CofG is behind your CofL (without any shifting of CofL). Presumably that is one of the reasons they considered this rear tank dangerous.
This is pretty much a description of AH's Mark I!
I'm right I'm right, I know I'm right, I need to test the CofG somehow...
-
I'd say the tail "lets go" too soon, but I'm no Spitfire pilot.
Read that ^ report Dolby. :banana:
-
"The Spitfire wing has washout and doesn't depart in that way. The root departs first and gives a clear buffet long long before the tips go."
Yes it does. The wash-out gives warning when the turn is tightened gradually but if you pull it too fast the stall will be total.
"A larger rudder is needed with added torque and thrust, you are implying it was a design flaw."
I'm not. It was determined that such rudder was adequate for keeping the plane flying straight and in normal power off stalls and it was, if you began the corrective inputs right away. In power on stalls and in spin if the tail got its inertia built up it was probably of little help.
"I think your reasoning is faulty. The significant change in this Mark IX was to it's CofG by way of the rear tank. Your view is not supported by the flight tests of normal (no rear tank) Spitfires I have read where they had to be held in a spin, letting go of the stick would allow the aircraft to correct itself."
By all means. If the aircraft has a tendency to stay in turn by itself or even tighten the turn itself it strongly indicates that in other than straight flight its MAC tends to move forward if its not there already, add some weight to the rear and the tendency is pronounced. Maybe that is why Spitty had rather big elevators, that is to keep it flying straight despite its CoG being aft of CoL.
"Look at the comments in your paper about the aircraft tightening up in turns. If the CofG is much farther to the rear than designed for then the tail is dropping harder in the turn and this causes an autonomous tightening of the turn. This makes it much harder to ride the turn and would make the aircraft more difficult to handle and more likely to depart unexpectedly. Then you are in a world of pain once departed because your CofG is behind your CofL (without any shifting of CofL). Presumably that is one of the reasons they considered this rear tank dangerous."
Yes, that is why I posted it, the point is in such unstable aircraft such condition was dangerous. However, such condition was hardly unique for Spitty. All I'm implying is that it was less manageable if the pilot lost control due to its inherent unstableness. As the CoG was moving forward in later versions such as IX due to bigger heavier engine, there was room, CoG wise, to make a rear tank as well, although it was advisable to empty it first before flying into combat...
Testing the Spitty 1 offline I found the power off stall to be just as described in existing documentation. In fact even a power on stall is surprisingly benign. I don't really see what is the problem? Accelerated stall? That is a totally different thing to stall tests conducted in normal flight testing.
-C+
-
The Spitfire wing has washout and doesn't depart in that way. The root departs first and gives a clear buffet long long before the tips go. A larger rudder is needed with added torque and thrust, you are implying it was a design flaw.
I think your reasoning is faulty. The significant change in this Mark IX was to it's CofG by way of the rear tank. Your view is not supported by the flight tests of normal (no rear tank) Spitfires I have read where they had to be held in a spin, letting go of the stick would allow the aircraft to correct itself.
The paper is useful but not in the sense you mean because I actually think it has added weight to this hypothesis. The non-standard rear tank moves the CofG rearward as it is filled and this Mark IX is demonstrating longitudinal instability during flight testing.
I expect the AH model to behave as described in real life which I contend it doesn't.
Look at the comments in your paper about the aircraft tightening up in turns. If the CofG is much farther to the rear than designed for then the tail is dropping harder in the turn and this causes an autonomous tightening of the turn. This makes it much harder to ride the turn and would make the aircraft more difficult to handle and more likely to depart unexpectedly. Then you are in a world of pain once departed because your CofG is behind your CofL (without any shifting of CofL). Presumably that is one of the reasons they considered this rear tank dangerous.
This is pretty much a description of AH's Mark I!
I'm right I'm right, I know I'm right, I need to test the CofG somehow...
washout is a design function intended to stall the Outer portion of the wing first to allow for recovery.
-
What has changed since 2011? http://bbs.hitechcreations.com/smf/index.php?topic=323289.0 (http://bbs.hitechcreations.com/smf/index.php?topic=323289.0)
I am beginning to think that it is more a case of simply flying too aggressively and pushing the aircraft way out of it's envelope. Unfortunately you don't get either that seat of the pants feel of the G, the change of wind noise or the control surfaces feedback that exists in the real thing, so it is too easy to push the aircraft too hard
-
what about the mark 5? while being an evolution the mark 5 feels perfectly equilibrated
-
What has changed since 2011? http://bbs.hitechcreations.com/smf/index.php?topic=323289.0 (http://bbs.hitechcreations.com/smf/index.php?topic=323289.0)
That discussion was about what to do after you've lost it.
I am beginning to think that it is more a case of simply flying too aggressively and pushing the aircraft way out of it's envelope.
I push everything too hard, I do this with every AH aircraft, consistently. The pilots in some of those accounts must have also been pushing hard too, with 109s on their arses and firing. Not one account I can find mentions the AH kind of departure. Furthermore disregarding the transition from real world to AH and back again only a few AH aircraft have this 'feel', which I know believe is best described as longitudinal instability. The Bf109 in AH is incredibly stable and self-correcting, I would describe it, and the Spitfire allegedly more so.
Yes, that is why I posted it, the point is in such unstable aircraft such condition was dangerous. However, such condition was hardly unique for Spitty. All I'm implying is that it was less manageable if the pilot lost control due to its inherent unstableness. As the CoG was moving forward in later versions such as IX due to bigger heavier engine, there was room, CoG wise, to make a rear tank as well, although it was advisable to empty it first before flying into combat...
Charge, I think we need to clarify a point as you seem to be implying that the Spitfire was unstable. I can't find anything in the literature to support that idea, quite the opposite. Even after departure you get the impression the aircraft would correct itself. Can you explain where your opinion comes from regarding this?
The specific instance of instability discussed in your report results from a rearward shift of weight and hence CofG in a uniquely modified Spitfire. The report of this modified Spitfire Mark IX is freakishly similar to the feel I get when pushing the Spitfire Mark I. I take this as further evidence that I'm onto something.
Being unable to escape from a spin I cannot find any reference to, no warnings about in manuals, no anecdotes of such in any of the material I read. I admit my library isn't exhaustive but the hypothesis sounds reasonable and even supported by Charge's report.
Is there some kind of community resistance or bias to finding or correcting a fault in this model of which I am not aware?
-
"Is there some kind of community resistance or bias to finding or correcting a fault in this model of which I am not aware?"
You mean..like...Luftwhining?
-C+
-
You mean..like...Luftwhining?
I don't know you tell me. Still waiting to hear where your apparently isolated opinions about Spitfire handling originate.
Please just everybody watch this video in fullscreen and think does the centre of gravity appear to be in the right place?
http://www.youtube.com/watch?v=BoQRbhR7Fgk
-
I don't know you tell me. Still waiting to hear where your apparently isolated opinions about Spitfire handling originate.
Please just everybody watch this video in fullscreen and think does the centre of gravity appear to be in the right place?
http://www.youtube.com/watch?v=BoQRbhR7Fgk
its funny how the tail falls first :noid
-
I think it's more that the tail stays down which is odd.
There's nothing significant aft of the CoL to account for this and if the first Mark of this type was so bad in real life it would have never been developed right through the war. Sorry, I know the Spitfire is hated here, as are the British by a lot of people, but Reginald Mitchell was a design genius and an experienced one at that by the time he penned the Spitfire.
Please look into the CofG and see if there's an issue.
-
"Sorry, I know the Spitfire is hated here, as are the British by a lot of people"
That is a childish accusation. I don't know any such people on this BBS.
"Reginald Mitchell was a design genius and an experienced one at that by the time he penned the Spitfire."
There is not really nothing special about the Spitfire. It had a large wing which had to be designed and manufactured carefully to negate the effects of its size. The problem with such design was that it was not really suited for mass production and after all it did not really offer anything a simpler design could not have achieved as well. Of course the design is visually appealing and the Spitfire is possibly the most beautiful fighter of WW2, but it was not "magical" -if you get what I mean. It had its drawbacks as any other design and what bugs me is that in this kind of simulation it can utilize all its pros and none of its cons, or maybe one, the one you are trying to promote to be taken away.
What comes to flight testing the stall behavior was measured by cutting the throttle and pulling the a/c into a stall, from level flight, and recovered, and that's what was reported and that is how I tested it, power on and power off and it performs normally. IRL It was NOT pulled into a vertical climb, power cut, and made the aircraft fall prettythang first towards the ground! The results of such test do not surprise me at all. The point is, as I stated earlier, that the MAC may be prone of shifting forward if the flow direction is not what is supposed to be and it seems that is what happens in the tail slide, and that is mainly because of elliptic planform.
-C+
-
That is a childish accusation. I don't know any such people on this BBS.
Why would you notice it, you're Finnish aren't you?
There is not really nothing special about the Spitfire. It had a large wing which had to be designed and manufactured carefully to negate the effects of its size. The problem with such design was that it was not really suited for mass production and after all it did not really offer anything a simpler design could not have achieved as well. Of course the design is visually appealing and the Spitfire is possibly the most beautiful fighter of WW2, but it was not "magical" -if you get what I mean. It had its drawbacks as any other design and what bugs me is that in this kind of simulation it can utilize all its pros and none of its cons, or maybe one, the one you are trying to promote to be taken away.
I didn't ask for your opinion about the design, I asserted that the designer would not have made a schoolboy's with the CofG and CofL and if he had and it was this bad it would never have become the primary fighter aircraft of Great Britain for as long as it was.
What comes to flight testing the stall behavior was measured by cutting the throttle and pulling the a/c into a stall, from level flight, and recovered, and that's what was reported and that is how I tested it, power on and power off and it performs normally. IRL It was NOT pulled into a vertical climb, power cut, and made the aircraft fall prettythang first towards the ground! The results of such test do not surprise me at all.
Irrelevant. Take other Aces High aircraft and perform the same test. Most of them recover by themselves (a few notable exceptions which had known issues). The test is especially relevant since this aircraft was noted for its docility of handling and self-recovery and our Mark I is demonstrably not so.
The point is, as I stated earlier, that the MAC may be prone of shifting forward if the flow direction is not what is supposed to be and it seems that is what happens in the tail slide, and that is mainly because of elliptic planform.
Have you got anything to support your MAC-shifting theory? Any evidence or flight testing etcetera, or is it just your personal theory?
-
All I've ever heard from pilots who flew the Spit is that is was a viceless aircraft in the air. Now, that is of course a truth with modifications if you push it well beyond its envelope, like we tend to do in this game.
-
All I've ever heard from pilots who flew the Spit is that is was a viceless aircraft in the air. Now, that is of course a truth with modifications if you push it well beyond its envelope, like we tend to do in this game.
I agree, now put this comment into context within the confines of Aces High: we also have the Fw190, which does not do well when pushing the stall envelope, then at the other end of the spectrum we have the Vought Corsair which by all accounts had nasty stall characteristics in real life, yet I think it is fair to say is very docile here. Then the Spitfire, which even in its earliest form is described as you say. Where on the Aces High spectrum of docility should it fall? Where does it fall now?
-
Actually, that's a different issue. The departure characteristics of the Fw190 and F4U were regarded as bad because they gave little or no warning to the pilot before stalling a wing, not because they were hard to recover from a stall. Stalling a wing in either aircraft would result in a snap roll which was lethal at low altitudes (like when trying to get back onto the deck of a carrier). How these aircraft compared to the Spitfire in stall-recovery or in "post-stall maneuvering" I do not know.
-
Actually, that's a different issue. The departure characteristics of the Fw190 and F4U were regarded as bad because they gave little or no warning to the pilot before stalling a wing, not because they were hard to recover from a stall. Stalling a wing in either aircraft would result in a snap roll which was lethal at low altitudes (like when trying to get back onto the deck of a carrier). How these aircraft compared to the Spitfire in stall-recovery or in "post-stall maneuvering" I do not know.
Perhaps what I said was misleading, I was referring to departure as well as recovery and I thought I read that neither of these aircraft had what could be described as any 'self-correcting' attributes at all. Again, I read that the Spitfire had to be held in a spin as neutral controls would allow the aircraft to recover itself.
Look, all bias aside, the Spitfire Mark I isn't what I'd consider my main ride and I do not discriminate against German aircraft either. It's just this thought occurred to me during a recent discussion during the BoB scenario. I did some reading and formed this theory about the centre of gravity being in the wrong place.
Please tell me at least one other person did some flight testing while considering this hypothesis?
-
I've been reading a little bit about the Spitfire to see if I could find any real life accounts which match the handling characteristics of our in game version. Specifically I was looking for info regarding the virtually unrecoverable flat spin and inverted flat spin AH's Mark I enters so readily. I can find no mention (although my Spitfire library is hardly extensive). The aeroplane is consistently referred to as docile, pleasant to handle and forgiving. Surely a far cry from what we have.
I then read up on spins and contributing factors and formed a theory / question:
Does AH's Spitfire Mark I have its centre of gravity too far aft?
:airplane: The C.G. generally speaking moves to the rear with fuel burn. That is why you burn the fuseledge tank first in a P-51, so that the C.G. doesn't inhibit maneuvering in combat. I would suggest that you run some stall tests with full fuel, then land, take up 25% and do the same stalls. It might be enlighten to you about what the difference is.
-
The Spit 1 has it's tanks behind the pilot. Loss of fuel should move the CG forward surely.
-
Spit I had its tanks forward of the cockpit. Marked D and E here:
(http://freespace.virgin.net/john.dell/spitfire_cutaway_diagram.gif)
I have too little knowledge on the Spit I's departure characteristics to make an informed opinion, so I'll leave that to those in the know. I will however add that the Fw190's reputed bad departure characteristics were only in accelerated stalls; the stall came suddenly and virtually without warning, but all that was needed to recover would be to center the controls (just like with most aircraft). At very low altitude this was lethal however as you would often find yourself in an inverted dive after recovery. In a normal (non-accelerated) stall from low speed (like in a typical landing situation) the Fw190 gave ample warning with intense pre-stall buffeting before it gently dropped a wing.
-
I've been flying the Spit I a lot lately and the only problem I notice is the occasional inverted flat spin. If you stall trying to go over the top and the engine dies there's no more power to pull you out of it and trying to manage the airflow to do so is difficult at best. I suspect in real life they didn't push the envelope that hard. It just happened to me two nights ago and I ended up having to bail.
-
The Spit 1 has it's tanks behind the pilot. Loss of fuel should move the CG forward surely.
:airplane: Spit fuel cells were in front of the cockpit and with the loss of weight in the frontal area, the moment arm, being influenced by the length of the fuseledge, causes the C.G. to move to the rear. If I am correct, I think the distance of travel for the C.G. was 8 inches, beginning at the canopy brace where the canopy and wind shield came together. You can generally tell where the C.G. is located, by looking where the main spar is located in relation to the cockpit in single engine aircraft. The 8 inches of travel for the C.G. is measured to the front of the wind screen.
-
I've been flying the Spit I a lot lately and the only problem I notice is the occasional inverted flat spin. If you stall trying to go over the top and the engine dies there's no more power to pull you out of it and trying to manage the airflow to do so is difficult at best. I suspect in real life they didn't push the envelope that hard. It just happened to me two nights ago and I ended up having to bail.
Have you tried extending the landing gear? Every once in a while, I can get the nose to drop enough to regain control by doing this.
-
There was a diagram showing them behind it, I guess the one I looked at was misleading.
-
washout is a design function intended to stall the Outer portion of the wing first to allow for recovery.
I thought it's just the opposite of that. Washout makes the angle of attack of the outer portion of the wing less than the inner. Wings stall when the angle of attack goes beyond a certain limit so with the angle less on the outer portion of the wing than the inner, the inner will stall first. This is done so the outer portion of one wing doesn't stall first causing a rapid roll to that side (tip stall). At least that is how washout is described for designing model airplanes.
-
You are correct. Also when you employ flaps it increases the effective washout so you have more aileron control into the stall.
-
There was a diagram showing them behind it, I guess the one I looked at was misleading.
Long-range PR Spits had additional tanks behind the cockpit and in the wings. Regularly flew to Berlin and back.
(http://www.spitfireperformance.com/spitfire9-fuelsystem-lr.jpg)
-
Long-range PR Spits had additional tanks behind the cockpit and in the wings. Regularly flew to Berlin and back.
(http://www.spitfireperformance.com/spitfire9-fuelsystem-lr.jpg)
:airplane: You keep impressing me with all this info you come up with and post for us guys! THANKS :salute
-
our mark1 is a PR model ! scandalous
-
:airplane: You keep impressing me with all this info you come up with and post for us guys! THANKS :salute
You're welcome :salute