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Discussion in 'Aviation' started by GregP, Jul 4, 2013.
Here are a couple of roll comparison charts:
Nice Greg. Thanks for posting. I have never seen the second graph before. I'ts back to making some additions to my roll charts.
Yeh, I have some good roll charts in Excel from graphs like these, and some decent numbers for Japanese aircraft perfomance in speed and climb ... but no roll. I forgot Kutscha is PNG in here and posted it for him in another forum, too.
Just shows how important having some strength was. From memory the top chart is with a max of 50lb effort, while the lower one is 30lb.
Makes quite a difference.
I believe you are correct, OldSkeptic.
The thing is, almost any healthy pilot fighting for his life can exceed a 50-pound pull when he needs to, possibly except when trying to roll a Bf 109 ... there isn't enough room in the cockpit to get a lot of roll force on it. It would be interesting to see at what maximum speed something like a 50-pound pull or push resulted in full deflection of the control surfaces .... but I haven't seen that anywhere. Also, the late model P-38J's and later had hydraulically-boosted ailerons (our P-38J does NOT have the boost, but the flying H-models do. Whether or not they use it today is unknown to me. The valve for boost is selectable to on or off) and could roll MUCH quicker than the unassisted P-38's which all have armstrong power ailerons ... how strong are your arms?
Another intangible is stall warning. In a Spitfire, Hurricane, and Bf 109 (and others) the pilot had a good stall warning buffet. In the Fw 190, there was NO warning; it just snapped into the stall when separation happened according to many references. That would suggest to me that if the Fw 109 were being flown by a competent pilot, it probably COULD turn at 14° per second. However, if the fight got low and the pilot wasn't competent at low-level hard turns, then the Fw 190 probably could NOT get 14° per second turn rate since the pilot would be allowiing himself a safety factor above the stall for survival. Nobody wants to be a smoking hole in the ground.
Not saying that was so. I am saying it makes sense that if the stall warning is very light, the pilot likely would avoid the limits of the envelope at low level unless he was desperate and thought he'd be killed unless he tried his absolute best. In which case, he might easily snap into the ground when the stall broke if he pulled a bit too hard.
So, though we have some charts for various characteristics, we don't seem to have a good representation of max performance in roll or turn rate or pitch rate, etc. and I doubt you will find any two flight reports that say exactly the same numbers. Several of the British flight test report berween the Spitifre and Mustang, I noted the Mustang was allowed to pull significantly less manifold pressure than the Spitifre. Not saying there wasn't a reason other than politics, but when the USA flew comparions, I believe the Spitfires were allowed to pull whatever the manual said was the max recommended MAP. What I'd really like is to see data such as, if one aircraft were to be limited in a test in some manner ... why was it so limited?
So ... you DO have to read the small print to find out that the side pull was only 35 pounds or whatever. But people see the chart and assume that is the maximum you can get. Not necessarily so ... frustrating to someone who spent a career in the test business (electronic test, but test nonetheless). Our job was to find out the limits of performance for electronic circuits after assembly and it seems to me that finding it out for aircraft should NOT be that difficult ... but it IS.
My preferred method would be to take five flight test reports on the same plane variant, throw out the high and low number and average the remaining three number to get a representative number for the type for some datum like rate of roll at some particular speed and control force used. Unfortunately, finding five separate flight test reports for the same model and dash number aircraft is almost impossible in most cases. I also wonder how they measured the force used when trying for a quick roll. Hopefully it was better than a fishing scale tied to the stick from the fuselage side ... but I don't know.
I suppose we solider on as best we can with what we have.
Good points Grep and thanks for the mention of the 190's 'interesting' stall characteristics, just like the Mustang's one not a lot want to acknowledge that.
And exhaustion was a factor. A hard dogfight and you would be exhausted. Many Luftwaffe pilots in their accounts tend to not mention that (excepting Stilpeper of course) , some of the best RAF/USAAF ones do (though there are a lot that don't .. a certain person who later did things in a rocket powered plane comes to mind, supermen in their own minds).
In that great book about the Banff Strike wing, at the end when they got Mustang III escorts (P-51B), there was a story about a hard dogfight between the Squadron leader and a Fw-190, which he won, and then he got killed. Other pilots accounts was that after the fight he just flew straight and level. Obviously totally exhausted.
And agree about the Spit, Hurri and 109. For all their faults they were much more forgiving in that sort of extreme flight regime.
Bob Dole told a great one, when hard pressed "put everything down and left". Stick forward and left, rudder full left, the works. Basically an inverted diving spin.
How many planes nowadays could do that and recover (let alone not fly apart)?
We talk about modern fighters with their angle of attack, But I love Stilpeper's account of getting out of trouble by doing a very steep (60 degree) climbing turn with his flight getting away from a bad bounce by Spits. The Spits couldn't follow them. And they kept it up until they got clear then dived for home. Everyone underestimates those 109s, the later ones might have been a bit problematic, but the Es and Fs were just about as good as you could get in many flight regimes.
Try either of those in (say) a Mustang or a 190 and, if they held together, you probably would have be a hole in the ground. Shudder even thinking about a -47 or a -38....
I have a great article in a Mustang book about a pilot that advocated that (all left and down). Showed it, landed and the tail plane fell off in the crew chiefs hand....
The 190 probably would have never made the landing...
Sure a Spitfire can outmaneuver a 109 or 190, but for how long;
'I found myself directly over Le Touquet, and a little ship outside the harbour was throwing up a furious barrage of flak at me. While I was in the process of turning and twisting, dodging the flak, I was bounced by two 109s. They were a well disciplined pair, so stationed that one could take over the attack where the other left off. Soon they were joined by two more. Turning and twisting I took short, blind bursts at anything that went in front. It seemed no time before I heard the hiss. I was out of ammunition. I was still over the ship which was relentlessly tracing my course through the sky with its flak. The 109s pressed home their attacks with persistent vigour, one coming within fifty yards, firing all the way. Watching his tracer, I found myself trying to climb up on the dashboard. With one shuddering turn after another I was bathed in sweat. I had to keep my head spinning from one side to the other so that I could watch two at a time. Gradually a sickening dread came over me as my strength diminished. On the point of exhaustion, I was ready to give up when all at once they left me alone.'
'Inside the coast, a Focke-Wulf 190, its yellow nose glistening in the sun, went by on my side ... Banging the throttle through the gate, I peeled out of the formation and went after him. He was the sucker bait, and, as if he was thumbing his nose, he rolled gracefully over and streaked for the ground. I was where they wanted me, a-l-o-n-e. In an instant, two more came rocketing down from above with the leading edge of their wings rippling with fire. As they split up and took turns attacking, a wave of nausea came over me. Determined to sell myself dearly, I took chances on longer bursts as they went by. The shudder of my guns maintained my spirit but I knew that soon my six seconds of fire would be up. The next time I pressed my thumb I heard that sickening hiss. I was out. Gasping in my mask as I strained with the G, I worked myself towards the channel. Doggedly they kept after me. By the time I had managed to get ten miles off shore I felt myself greying out with exhaustion. I was ready to give up. Another was coming in. I leveled out, flew straight towards England and closed my eyes. After what seemed like an eternity, I opened my eyes and looked. On my port side was a 190 slowly going by. For a moment we looked at each other eye to eye. The next instant he was in a climbing turn and went diving back to France.'
Long enough to avoid being shot down, in spite of 4 to one odds in both instances. I'd like to see how long a lone 109 or 190 would last against 4 Spitfires under the same circumstances. (In neither case is the mark of Spitfire being chased mentioned - would hazard a Mk V as a guess.)
The Mustang stall is not that big a deal. If you let it develop, it can be a real issue, but you get a good warning and when the break occurs, release of backpressure has you flying again right away. I've ridden with a friend in his P-51 while he practiced for his Biennial Flight Review and he did stalls and stall approaches in both approach and departure configuration. When it shuddered, he simply relaxed a little back pressure and it was a non-event. We went up to 12,000 feet and did full stalls and he simply released at the break and we never wandered around much before returning to contolled flight with minimal altitude loss. If you are so inattentive as to allow it to rotate a full turn or more before you catch it, then yes, it can get to be a major event.
I don't know of any WWII fighter that has a problem making a 60° climbing turn, but perhaps I am simply misinterpreting your description.
True the Mustang was not cleared for snap maneuvers, but a snap roll isn't really a combat maneuver anyway ... for anybody, not just a Mustang. Someone might have escaped defeat with a snap roll, but I doubt anyone got a victory as a direct result of one.
Good point about the Bf 109. It had some glaring faults but was also near the top of the heap in many combat qualities and was always a strong climber. Some people might think that is a knock on the Bf 109's basic design and that is just not true. It simply means the few glaring faults COULD have been corrected by Messerschmitt if the RLM had allowed them the time to do so. We might recall that while the Germans started out on top of the world, victory-wise ... but by late 1942 - early 1943 they still had not replaced all their early losses. So a production interrruption of unknown duration to correct a known fault might not be acceptable ... just as Grumman was never allowed the time to correct the slow roll rate on the Hellcat here in the USA.
WWII taught us the importance of flying qualities. The US Mil-Spec on flying qualities of manned aircraft are an eye opener. If designers in the early to mid-1930's had known hopw important the stall warning and stall behavior was in low-altitude turning fights, I'm pretty sure they could ALL have tailored the stall characteristics to be better during development.
One indication might be that all of the last-generation piston fighters, the "pinacle of the breed," had decent stall characteristics and pretty good handling together with great power, acceleration, climb, and speed. So it IS possible to have a plane that is good everywhere, even if not the best everywhere.
Oh it was in the BoB, the 109 and Spit had very similar climb rates but the 109s was at a higher angle of attack and a slower speed. In Stilpeper's account he got his flight to keep it up for about a 10,000ft climb, eventually climbing away from trouble. The Spits couldn't match it, could for a short time but not long enough to get a hit before they fell away. Difference between a zoom and contineous climb.
And the difference between a lighter aircraft with a high wing loading against a heavier one with a low wing loading. The BoB Spit had the better wing loading, but the 109 had the better thrust loading (of that era, later models of both swapped about). Both were the kings of the climbers, albeit in different ways.
As for the Mustang, the P-51B/C were directionally unstable, especially at higher speeds:
Louis B Wait, Administrative Test Pilot, NAA, 8/8/1945.
Interesting that they changed the trim tab to a boost tab. I'll have to look at our Mustangs next weekend and see if the D models were trim tabs or boost tabs. I believe the D models have trim tabs off the top of my head but I have been mistaken before.
Interestingly, we are changing the trim tabs on the ailerons of our soon-to-fly Bell YP-59A into boost tabs. It only has ±13° of aileron up and down travel, and the extra aileron authority will help.
The degree to which an aircraft provides warning of stalls and spins and maintains a consistency of behaviour in different aspects, speeds and at different altitudes is a greatly underappreciated quality - perhaps because it is difficult to quantify. Speed, climb etc are easy to define in mph, fpm or whatever but the 'forgiveness' of an aircraft can be relayed only in pilots impressions. Nonetheless, it was vital. I think the Spitfire's great reputation as a fighter owes much to this intangible quality. Invariably it faced opposition and contemporaries that climbed, dived or flat out ran as well as it did, but time and again when pilots from both sides of WWII who have had the opportunity to fly a range of aircraft are asked 'what was the best fighter to fly?' they answer 'the Spitfire'. This ability to inspire trust and confidence in a pilot is an unquantifiable but very important quality in a high performance aircraft.
Well said Cobber. An aircraft thaht gives you warning of an impending stall before it actually stalls is a pleasure to fly near the limits. One that just quits flying without notification can be flown, but people will avoid the limits.
Knowing what we know now, maybe all the Fw 190 needed was some triangular stall strips near the wing root to cure it and provide buffet warning. Lacking that, maybe a few degrees of washout at the tips. Whatever, it COULD have been fixed and was probably a victim of the "we can't afford a production interruption" mentrality.
So true, that was the issue that killed the Spiteful. Might have been a bit faster but its stall/spin/etc characteristics were far poorer than a Spit.
Interestingly the pilot of the Mustang I flew in (in NZ) who was a very experienced aerobatic pilot and who had just came back from the US doing aerobatic flying with other Mustang pilots (my god I didn't know a plane could do that when I was flying with him) also flew the Spit XVI (unfortunately only a single seater) that was there in those days. And he said he preferred flying the Spit, pretty much for the reasons mentioned, it was easier to fly close to the limit. He said there were certain maneuvers he would do in it that he wouldn't even try in a Mustang (forgot what they were, very long time ago).
Though given how he threw that 51D around, after he asked me if it was ok to do 'some aerobatics', god only knows what they were .. I thought we did everything possible. Has to learn very quickly to breath in and hold before he started anything, cause there was too much G to breath in. Still remember it well.
There is a well known so-called expert on the Fw190 that says the the snap/spin of the 190 was due to incorrect aileron adjustment.
Hadn't heard that one Milosh. I suppose it COULD be true, but you'd think it would be noticeable to the pilot if the ailerons were reflexed upward in fight.
Since I won't be flying one, I could be mistaken there ... whatever, the Fw 190 was a remarkable aircraft right through to the end of the line.
My favorite was the Dora. I might have made the Ta-152C my favorite, but they never had the chance to work out all the Ta-152 bugs before the war ended, thus ending Fw 190 development. The Dora was a good, solid fighter that had decent, if not chart-topping performance. It wasn't the fastest plane in the sky but was heavily armed, rolled VERY well and was never to be taken lightly by any opponent, especially if the number of aircraft was near even.
Supposedly there was 3 variations of the aileron geometry (it been quite awhile since reading what the so-called expert said) and there was a jig fixture for setting up the ailerons correctly.
Keep in mind this so-called expert said there was only 16 squadrons of RAF fighters that used 100 octane fuel during the BoB.
You wouldn't think the ailerons would be designed to be taht complicated considering they were usually going to be maintained in some farmer's field out in the open.
I'll try to look around and see if I can find any corroborating data for that, but it's a new one on me so far.
Must have meant that the majority of 190s built had incorrect aileron adjustment?
Wonder if there is any thruth to this rumor of mis-rigged ailerons?
Steve Hinton has flown the Paul Allen Fw 190, the only original Fw 190 flying. His remarks were that it was VERY different from the Flugwerk replicas he had previously flown. He said you could tell you were a great plane right from liftoff. But he didn't say anything specific about the stall in the few comments he made. We were werewinding down the volunteer meeting ... and there was no question and answer period. Suffice to say he enjoyed it and would fly it again anytime Paul allows it.
Naturally, in his few fliights, he didn't push the limits to see how it compared with familiar mounts. The intent was to fly the test program, check the rigging, check the engine operation, check the propeller operation, make sure the systems were all operational, were operating correctly, and particularly, that there were no serious overheating issues. There weren't.
It flew quite nicely.