A newbies impression of the 109 and spit

[NZtyphoon]

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):

Part I Note A Flying Limitations
1. Introductory.
(i.) The Pilot's Notes for each type of aircraft lay down certain flying limitations. They state, broadly speaking, the demands which it is safe to make of the airframe. Non-observance of the flying limitations may lead to increased maintenance work, or, in extreme cases, to structural failure in flight.

(ii.) In the fixing of these limitations there is of course a margin or factor of safety allowed. This factor for airframes varies according to the degree of confidence with which their strength and likely stresses can be predicted, but is commonly around 2. This means, for instance, that a wing 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.

(iii.) The flying limitations also involve questions of safe handling from the aspect of controllability.

(iv.) In combat and emergencies pilots must take risks with their aircraft, balancing one risk against another; limitations must be strictly observed in so far as there is no sufficient reason to exceed them.

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.

4. Manœuvres not Permitted
(i.) Intended spinning of operational aircraft is permitted only in the case of certain approved single-engine fighters within the limitations stated in the Pilot's Notes. (Normal Methods will usually effect recovery - A.P. 129 Ch. III)

(iv.) The reasons underlying these prohibitions are partly considerations of aircraft strength and partly of control. Aircraft are designed to fulfill their operational role and not to perform manœvres of no operational value...

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

[winny]

Originally Posted by Kurfürst

As I understand and from RAE papers the installations of bob weights to the elevator and longitudal instability were related. To my best understanding - and do correct me if I am wrong - instability means that if you pull the controls (in whatever direction), the aircraft will not only change its roll/pitch/yaw to the extent of control movement, but also keep increasing it on its own, as if there were some kind of inertia/acceleration going on. This was noted on Spitfire Vs by the British.

By adding the bob weights and making the controls progressively harder to move for greater deflections, it made this increased acceleration problem more difficult to encounter.. It did not cure the instability itself, which was an inherent aerodynamic feature of the design, but made it harder for the pilot to make it happen.

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?

[Crumpp]

Can you explain to me how fitting a bob weight would correct an aerodynamic 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.

"suffers from quick changes of trajectory along the vertical axis, coming from high longitudinal thrust momentum, and significantly disturb aiming"

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

So was the impact of the inertia weight a double edged sword?

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

[Crumpp]

First, the Pilot's Notes were deliberately conservative to ensure that most pilots flew well within the limitations of the airframe

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

they were easy meat.

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:

wing 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.

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

RAF acknowledged that in combat it was up to the pilot to choose what risks needed to be taken;

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.

In combat and emergencies pilots must take risks with their aircraft, balancing one risk against another; limitations must be strictly observed in so far as there is no sufficient reason to exceed them.

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

The reasons underlying these prohibitions are partly considerations of aircraft strength and partly of control.

[JtD]

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.

[Kurfürst]

Originally Posted by winny

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.

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.

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.

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.

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?

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?).

[Kurfürst]

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.

[winny]

Originally Posted by Kurfürst

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.

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?

[Crumpp]

Pilot's who flew 'by the book' generally didn't last very long, on both sides

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.

You find me a rule and I'll find you someone who broke it..

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]

[Kurfürst]

Originally Posted by winny

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.

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.

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...

Mother Nature took care about enforcing it though..

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.

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'.

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.

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.