Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Wotan on May 07, 2002, 04:01:09 AM
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Impossible to Follow? (http://users.senet.com.au/~mantis/FW/Bob/Best.htm)
opinions?
did the 109
leading edge slats automatically deployed, with a loud bang clearly audible over the engine roar!
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I always thought the 109E was better than the Hurri I and Spit I in the first 270 degrees of a turn. And after that the spit/hurri would gain.
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That piece is a reasonable take on the subject. Opinions aside: This diagram (http://www.fourthfightergroup.com/eagles/spit109turn.gif) and this diagram (http://www.fourthfightergroup.com/eagles/spit109turn18.gif) should put an end to the never ending debate. It won't though ;)
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MW what version of 109 is in those charts? E-3, E-4, E-7, F-4?
Were test pilots familiar to using slats?
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me those are fantastic!!! you have more like that???
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spit 1 would definitely win if flown properly and with a constant speed rotol propeller. it can outclimb and out-turn the 109E
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Do the Clmax figures on this chart
http://www.fourthfightergroup.com/eagles/spit109turn.gif
mean that the 109 wing creates more lift then the spit? Would this translate to a faster instantaneous turn? Is the difference in induced drag the cause for the spit's sustained turn advantage and e-retention?
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MW - Wow Mikey!
Virage - Lift coefficient (CL) is the lift divided by wing area and dynamic pressure (proportional to the square of indicated airspeed). Bf 109 had quite high maximum CL figures but a very small area. The Spit's bigger wing means it will create more lift at the same CL and IAS.
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Those turn comparisons spit1-109E are based on CALCULATIONS. They are theoretical calculations, and not test flight data.
Look at the charts from mw´s page : "ASSUMED values of Clmax"
It´s funny anyway to see how many think that one captured 109E is representative for several hundred or thousand build.
niklas
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Niklas,
That flight envelope is based on real flight tests of the RAE. But Clmax values are calculated.
Gripen
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Don't know about real life, but I do know which plane out-everythings the other in a fight between a spit I and a 109E.
Speaking of which, it'd be nice to have the slats visually (or at least audibly) modelled. I've heard that they are modelled, but there really isn't any way to tell. I do know the plane is stable when behind another plane, although supposedly the slats would pop open and ruin stability.
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Urch, I think the slats were put in there to increase stability of aircraft performance, not decrease it.
From what I've read, much like the article Wotan suggested, the slat deployment was more of a psychological barrier to inexperienced pilots rather than physical barrier of the plane. A newbie's gotta be scared when he's sweating all over in a tight turn and then suddenly a *bang* and a *shake* ;)
Another problem seems to be the assymetrical extensions and retractions, which stabilized the plane in near-stall situations, but kept ruining the gun solution.. *bang* *ploop* *bang* *ploop* everytime the air speed went up and down in turns.. :D
I think I've read somewhere this assymetrical deployment was fixed in latter version 109s..
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Another thing AH doesn't model correctly in the 109 is that the whole vertical stab and elevator moved when the aircraft was trimmed. It was not only the elevator like we see in AH. It might give the 109s some disadvantage in that aspect not to be able to move the whole vert stab while in high speed dives.
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I rather had the opinion that the 109 pilots in the Battle of Britain were rather experienced, ore atleast more experienced than their opponents from the RAF anyway.
Anyway, the slats were a nice reminder that the aircraft was close to stalling. While it was a good thing that they "took over", one would still know that there was not so much a space any more for error, and unlike the Spitfire, the 109 could be forced into a nasty snap, slats or no slats.
But generally putting it,,,,giving the same amount of thrust to each of the opponents, the Spitfire would definately be the winner of the turnfight, maybe even also climb and run;)
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Atually Angus all I have read about the Bf109 suggested it had very benign stall characteristics with no tendancy to snap like the Fw190 is known for. In fact some said the Bf109 was perhaps too stable for a fighter.
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Originally posted by Kweassa
Urch, I think the slats were put in there to increase stability of aircraft performance, not decrease it.
From what I've read, much like the article Wotan suggested, the slat deployment was more of a psychological barrier to inexperienced pilots rather than physical barrier of the plane. A newbie's gotta be scared when he's sweating all over in a tight turn and then suddenly a *bang* and a *shake* ;)
Another problem seems to be the assymetrical extensions and retractions, which stabilized the plane in near-stall situations, but kept ruining the gun solution.. *bang* *ploop* *bang* *ploop* everytime the air speed went up and down in turns.. :D
I think I've read somewhere this assymetrical deployment was fixed in latter version 109s..
I understand that the slats were there to enhance stability- but one of the side effects was they made the plane unstable in a firing solution by banging out assymetrically. This is a well documented 'feature' (as opposed to a bug lol) of the slats on the 109- and that behaviour is not present on any of our 109s.
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Grunherz;)
Just read today that the Spit could not be pushed into a snap.
here it is: (hence the teaser)
"Flying the Spitfire was like driving a sports car. It was faster than the old Hurricane , much more delicate. You couldn't roll it very fast, but you could make it go up and down much easier. A perfect lady. It wouldn't do anything wrong. The Hurricane would drop a wing if you stalled it coming in, but a Spitfire would come wafting down. You couldn't snap it into a spin. Beautiful to fly, although very stiff on the ailerons - you had to jam your elbow against the side to get the leverage to move them. And so fast!!! If you shut the throttle in a Hurricane you'd come to a grinding halt; in a Spitfire you just go whistling on.
[1] P/O H.G.Niven 601 & 602 Squadrons, having flown both Hurricane and Spitfire. "
Sort of a paradox to what happened to many a Spit pilot who "Spun in"
Anyway, the 109 was much more "stable" on the vertical axis than the Spitfire, and doubtlessly a lovely balanced aircraft within a certain speed envelope. However with double the wing loading of the Spitfire, it could be pushed beyond the limits.
Actually I heard the thing about the "snap" from Gunther Rall.
He said that if you would try to push the 109 too far, it would eventually snap, while under the same cirkumstances, the Spitfire would not.
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Every plane has "limits" and the plane can be pushed beyond them. Even the Spitfire has horribly high winglading compared to lets say an Extra 300. It's all relative. :)
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Hi MW,
Great diagrams! I didn't know they came that close to energy manoeuvring in WW2 :-)
Though it doesn't affect the instantaneous turns, the Me 109E example the RAF tested might not have been entirely up to the manufacturer's specifications with regard to power. I think at 12000 ft, it should top out at closer to 345 mph than the 335 mph indicated in the diagram you posted. This indicates that it was probably lacking quite a bit of power, adversely affecting its low-speed sustained turning ability (which is one area of inferiority, according to the RAF tests).
However, in general, can be no doubt that the Spitfire I generally outturned the Me 109E. Galland in "The First and the Last" describes how the Luftwaffe pilots were frustrated by the Spitfire's manoeuvrability until Mölders and Galland devised high-speed tactics to counter it. Quite opposite to what was stated in the article referred to above, it was the reluctance of the Luftwaffe pilots to turn that made the RAF think they didn't trust the strengths of their planes. Far from it - but turning would have given the advantage to the Spitfire which was superior in this area.
Even Galland's comment "I'd like to have a squadron of Spitfires" aims at the different strengths of both planes. Galland believed the Me 109 was the better fighter plane, but he knew that by following Göring's orders and flying close escort for the bombers, they'd get caught without height or speed advantage so they'd have to rely on defensive turning - and that was the Spitfire's strength, not the Messerschmitt's.
Regards,
Henning (HoHun)
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HoHun,
Actually flight envelope concept was known long before war. So far I have found/seen (flight tested) flight envelopes for: Spitfire I, Bf 109E, F2A, P-51, P-47, P-38 and F4U.
IMHO speed/g-load diagram is easier to use than turn rate /speed diagram.
gripen
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Ho-hun: Top level speed for the 109E was found to be 355 mph at 16,400 ft. In fact the RAE report states that the "top level speed agreed well with the published figure" (in Germany). I have quite a number of trials reports related to the 109E. I've seen no mention of the engine being underpowered or having problems. The report did mention that the radiators were opened up to 13,000 ft during the climb tests for cooling , which explained the discrepancy with the German figures in times to height. (Interesting side note; Supermarine ran their climb tests with radiator closed too, whereas the British testing establisments opened them for their climb figures). Hmm, actually 335 mph at 12,000 ft. seems about right to me. Perhaps more relevant would be the 1200 B.H.P at 12,000 ft. posted. Does this seem correct to you? For comparison purposes the British were quick to point out that the DB601N used in the 109F they tested did have problems and the figures should be "treated with reserve".
I'm surprised no one picked up that the Spit was only running at +6.5 lbs/sq. ft. Running at +12 lbs. with 100 octane fuel would increase the power of the Merlin III by about 25% at 12,000 feet, according to the engine charts I have. Now that would make a difference ;)
funked :)
Zig, yea, I have more ;)
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Hi Gripen,
>Actually flight envelope concept was known long before war.
Yes, but I was referring to the lower diagram in figure 18 which actually maps specific excess power.
(The other application for specific excess power diagrams I know from WW2 are the climb diagrams for the Me 262, which established the standard method for graphical climb optimizations for jet aircraft.)
>IMHO speed/g-load diagram is easier to use than turn rate /speed diagram.
I agree! I guess the turn rate diagrams are predominant because turn rate was considered a key parameter until the 1960s, when excess power took over.
Regards,
Henning (HoHun)
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HoHun,
Ah, I missunderstood your point. Anyway, that "angle of straight climb" in the flight envelope is very handy and you can see relation between it and excess power.
gripen
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Even Galland's comment "I'd like to have a squadron of Spitfires" aims at the different strengths of both planes. Galland believed the Me 109 was the better fighter plane, but he knew that by following Göring's orders and flying close escort for the bombers, they'd get caught without height or speed advantage so they'd have to rely on defensive turning - and that was the Spitfire's strength, not the Messerschmitt's.
I was always under impression he wanted those spitfires for training and mockfight purposes. And eventually got few which were rotated around fighter bases to educate pilots of spitfires handling.
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heres AG himself explaining what he meant
AG wav (http://members.aol.com/geobat66/galland/galland.wav)
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From Wotan's link:
"Add to this that even similar aircraft vary in performance from example to example, and it is no wonder that performance comparisons are so difficult and opinions are so varied!"
I wish more people would remember this when squeaking about plane performance.
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What is the 'Corrected Airspeed' at the bottom of MW's charts?
Vi (indicated airspeed?) - something. ??
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>>IMHO speed/g-load diagram is easier to use than turn rate /speed diagram<<
There are several ways of showing energy performance. Your preference is one that is common in EM texts.
Just as common is the chart that substitutes turn rate for G. This chart is particularly useful when constructed as a "differences" chart...meaning, a chart that combines the performance values for two aircraft on one chart. In doing so, meaning comparisons can be easily seen.
The same can be done when using G...but the intuitive lessons learned are not as obvious.
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Andy,
Well, there are two reasons why I prefer V/g presentation in the case of the WWII fighters.
1. It is a direct flight envelope and WWII fighters could be maneuvered only inside flight envelope, outside envelope (in stalled or buffeting areas) they were more or less out of controll. Current fighters can do maneuvers outside conventional flight envelope, so in that case turn rate aproach might be better way to present turn performance.
2. With V/g diagram connection to the size of the turn circle is also a bit straighter. In the continous turning attacking fighter must turn inside target (ie should do smaller turning circle) to get to the firing position despite what ever continous turn rate it could reach at higher speed.
Anyway, both ways do the job. All war time presentations I have seen are V/g diagrams, current presentations are mostly turnrate based.
gripen
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If this is a little confusing, here are two EM charts...one for a F-4, the other for a MiG-21.
The MiG chart uses airspeed and turn rate as the axes, while the F-4 chart uses airspeed and G.
The curving lines inside the envelope that have plus or minus signs show how much excess energy the planes have at any point. Plus means the airplane at that G and airspeed can still accelerate or climb...the minus sign means that the plane is losing speed at that G and airspeed. The zero line (known as the "zero Ps" line) is the place where the plane can sustain its G at the given airspeed.
Which type of chart to use is mostly a matter of individual preference.
(http://webpages.charter.net/alfakilo/b1.jpg)
(http://webpages.charter.net/alfakilo/b2.jpg)
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Andy,
IMHO that F-4 chart is more clear and thats the way I prefer it, no need to argue about that. Anyway, the F-4 and MiG-21 are that conventional fighters which could not maneuver outside conventional flight envelope. I mean planes like the F-16 which can do stalled maneuvers (outside conventional flight envelope).
gripen
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Hi MW,
Sorry for the late answer - I spent quite some time trying to convert the Me 109's wing loading in lbs/sq ft to boost pressure in ata. It took me a while to realize ... ;-)
>Perhaps more relevant would be the 1200 B.H.P at 12,000 ft. posted. Does this seem correct to you?
Actually, it seems to be a bit too much :-) The DB601A engine chart I've seen (undated - might be 1937 numbers) says 1005 HP at that altitude. Take-off power was 1100 - 1200 HP with a maximum altitude to 500 - 1500 m. This was limited to 60 s - enforced by a clockwork timer.
(I don't think the RAE actually bench-tested the engine, so it may be a nominal value anyway.)
>I'm surprised no one picked up that the Spit was only running at +6.5 lbs/sq. ft. Running at +12 lbs. with 100 octane fuel would increase the power of the Merlin III by about 25% at 12,000 feet, according to the engine charts I have. Now that would make a difference ;)
The Me 109E and the Spitfire I/II were subject to constant modifcations. Do you think it would be possible to recognize the exact equipment and engine status of the tested Spitfire from the weight and power data?
From the use of +6.5 lb/sq. in. (sq. ft. is for wing loadings, ask me :-), I'd say that the Spitfire was in the condition prior to the release of 100 octane fuel in March 1940?
Regards,
Henning (HoHun)
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Sorry HoHun, but something must be getting lost in the translation. I think your criticism is that I mistyped ft. for lbs.? If so you'll be pleased to know that the the bloke who drafted the chart made an error when he wrote B.H.P - 1200 on the 109 portion of the chart. The text of the reports show 1100 hp as max power at 2400 RPM at 12,000 ft.
>Do you think it would be possible to recognize the exact equipment and engine status of the tested Spitfire from the weight and power data?
Well, yes, in allot of cases for Spitfires I could. Of course I have all the reports that show condition of planes and weights and loading, so I'm somewhat familiar with the numbers and they have meaning to me.
Frankly the +6.5 lbs/sq.in. is in white on black in the chart. Sorry, but is was just so obvious to me. Futhermore, two reports I have with that first curve specify that fuel used was 87 octane. I apologize for not sharing that information earlier. It wouldn't have changed the basic premise that the Spit I could out-turn a Me 109E though.
All this doesn't alter my view that it likely wasn't the 109 that was not "entirely up to the manufacturer's specifications with regard to power", but rather its a certainty that BoB Spit Is had more power than that chart shows.
"The Me 109E and the Spitfire I/II were subject to constant modifcations." Yes they were. The charts are an interesting snapshot in time. I know the 109E7 had more power as did the Spit II. But I've no interest playing that game out. I should think that what would be of the most interest to people on this board would be representative performance of the BoB era varients. I can shed some light on that, but guess what...I dont have all the answers myself.
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Hi again HoHun:
>I spent quite some time trying to convert the Me
109's wing loading in lbs/sq ft to boost pressure in ata. It took me a while to realize ... ;-)
I wasn't sure if you were being serious or not with that comment. The following info may be of interest and may, or may not, help your case:
Top Level speed 109:
355 m.p.h. at 16,400 ft., 2400 r.p.m. +2.3 lb/sq.in. boost pressure. Radiators closed.
From another report:
Take-off power: 1175/2500
Rated h.p. at 2400 r.p.m. at 3.75 lb/sq.in. boost pressure at 15,000 ft. : 1100
Power loading: (lb/b.h.p) 5.07
Wing Loading: 32.1
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MW, I noticed you've been posting here alot more recently.
Nice info and flight test data you keep posted on your website.
You flying here now?
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There are several versions of RAE Bf 109 reports around, mw'sversion seems to be from the PRO. After war Aeronautical council published huge amount of RAE reports and these versions are very clear and neat. Luckily they published Bf 109 report too and it should be easy to find a copy from technical libraries around Britain, mine is ordered from the British library.
gripen
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Hi MW,
>I think your criticism is that I mistyped ft. for lbs.?
No, I really, honestly mistook the wing loading value for the boost pressure and got confused by that. I noticed your typo meant that you came close to making the same mistake, but unlike me managed to avoid it :-)
>The text of the reports show 1100 hp as max power at 2400 RPM at 12,000 ft.
Ah, that seems more likely. As I said, my engine chart indicates even less than that, but it's not dated, and I guess it's possible the engine got uprated to the values indicated in the report.
>Sorry, but is was just so obvious to me. Futhermore, two reports I have with that first curve specify that fuel used was 87 octane.
Roger on 87 octane, it leaves a lot of potential for the Spitfire.
>I should think that what would be of the most interest to people on this board would be representative performance of the BoB era varients.
Certainly! That's why I'm asking for the exact configuration - the Spitfire was in a pre-Battle of Britain configuration obviously, and (not knowing the date of the report), I'd imagine that the Me 109E probably was captured and tested before the Battle of Britain as well, or they'd have used a Spitfire running on 100 octane as reference.
Regards,
Henning (HoHun)