improving the 109??

[drgondog]

A couple of points - with the decision going to Greg.

1.) The LE Slats deploy when the adverse pressure gradient tickles the stall aft of the slats. At this AoA the inboard wing is already in Stall or impending stall condition

2.) A high AoA is required to initiate the slats but in a turn the wings are in asymmetric loading with the high wing leading the action (aileron down, effective chord to V freestream at greater effective angle of AoA). This is THE source for all 'Snatching" comments, particularly from Rall, leading to temporary yaw if not controlled.

3.) The 109 W/L was inferior to the Spit and superior to the Mustang and FW 190 and Tempest - but less than a couple of percent. Wing Loading and level flight CL are the major considerations in comparisons - but the level flight C/L is NEVER attained in a turn. In the example of a 109 with Slats deployed, it has already reached local stall inboard and the CL for the airframe is neither predictable nor easily reproduced - hence "It ain't part of the Flight Test Plan"

4.) The level flight drag of the 109G was 10% higher than a Spit and nearly 65% greater than the Mustang.

5.) The drag due to AoA was also far higher that either the Mustang or the Spit, and the Spit was the best of the three.

6.) any comparison discussions have to be considered in the context of altitude, boost conditions framing the Thrust parameters, airspeed, Power Available vs Power Required (which has rapidly diminishing 'Delta' in any turn - but worse for the 109 that the other two). Major complications in performance model arise when developing and factoring the Form Drag due to AoA (large), the Powerplant/prop efficiency in the full range of speeds encountered in curved/circular flight path, the stall characteristics in asymmetric flight, the trim drag of the rudder deflections and aileron deflections. These are entirely left out of the discussion in Aero courses due to a.) lack of data, and b.) non-linear nature of each factor.

James W. One of the quotes (in the LW interrogation section-1945 "Spitfire vs 109" link) from one of the Interrogations focused on the general high performance of the Mustang vs the 109, in which the interviewee stated that only the best and most experienced pilots should engage in turn combat with the Mustang - and never with the Spitfire.

7.) all the VVS data often quoted in these discussions are below 2K meters and Most if not all the ones I have seen presented in this forum are pre 1943, with some lapping into early 1944.

 

[pbehn]

i dont know why they put guns on Bf 109's the should've just saved the weight, avoided the RAF with their superior speed, climb, height and maneuverability and waited for the Spitfire pilots to kill themselves on landing as it was such a danger to do

Dowding was ahead of the game, all spitfires were grounded as a last desperate measure while the pilots farted in the direction of Calais.

 

[GrauGeist]

An observation that I'd like to make:
The majority of aircraft tested weren't just pulled off the front lines nor were they being tested under combat conditions where they may have already burned off a certain aount of fuel or had just been in a scrap a few minutes before, sporting holes from a close call with an adversary - all of which would effect performance.

Were the pilots in the test tired from already flying a sortie earlier that morning? Did they have partial ammunition loadouts? Were the engines already halfway through their maintenance schedule? Was the much-needed plane cobbled together from other airframes to keep it in the fight? Was there mud amd dirt on the plane's surfaces and perhaps crap stuffed into the wheel-well, keeping one of the maingear from retracting 100%

In otherwords, the majority of these tests were under controlled circumstances with fresh or prime examples of the type.

However, real-world performance was a crap-shoot with a great deal of random input on the aircraft's performance, including the condition of the pilot, who may have already flown one or two missions that morning, may have been kept awake all night by harassment bombers and such. (In the PTO, many of the pilots were suffering from tropical diseases, too)

 

[pbehn]

However, real-world performance was a crap-shoot with a great deal of random input on the aircraft's performance, including the condition of the pilot, who may have already flown one or two missions that morning, may have been kept awake all night by harassment bombers and such. (In the PTO, many of the pilots were suffering from tropical diseases, too)

And by the same measure captured aircraft under test were not serviced and prepared by qualified crew until the end of the war.

 

[GrauGeist]

And by the same measure captured aircraft under test were not serviced and prepared by qualified crew until the end of the war.

Yes indeed.

So even under the best controlled circumstances, where one type may have an edge over another type, real-world circumstances may dictate an opposite result.

 

[rochie]

Yes indeed.

So even under the best controlled circumstances, where one type may have an edge over another type, real-world circumstances may dictate an opposite result.

I agree Dave.

But there is no point in telling your pilots
"look chaps weve tested the enemy aircraft and if one gets behind you do a max sustainable turn as he cant turn inside you and it'll give a few seconds to think"
if its not true and the first time one of your guys is in trouble he does as you say and is shot down because the enemy can turn tighter !

 

[stona]

Technicians from all countries were perfectly capable of 'servicing' foreign aircraft, at least to the point of restoring them to flight or keeping them flying until some vital and unavailable part was required. A German looking at a Spitfire, or a Briton looking at a Bf 109, were not going to see anything they didn't understand.
I said that such tests are not definitive because there are many variables, not least a test pilot who would be relatively unfamiliar with the enemy machine. Nonetheless the data obtained is valid and it was used to develop fighting tactics for use against the various enemy types.
Douglas Bader was a man like Marmite, you love him or hate him, but for all his qualities and failings he was smart enough that the first thing he wanted to do, when he became aware that the RAE had acquired a Bf 109 F was to fly it and establish its qualities for himself.

He makes the point that 100s of hours of data collection are not needed, just the assessment of a few experienced pilots. They didn't need to establish the exact radius of turn of the aircraft at all sorts of altitudes and speeds, just whether they could turn inside it!
His suggestion that Wing Commanders, Flying be given first go was surely influenced by his position as precisely that

Cheers

Steve

 

[GrauGeist]

It's certainly is a tremendous help to know the enemy's strengths and weaknesses and testing captured aircraft provide a wealth of information that can be better used to get the upper-hand on an adversary. If that data saves one pilot's life, then it was a success.

But the discussion on aircraft values often comes down to the "this type had a .001% advantage over that type because test results proved etc. etc. etc."

 

[stona]

Margins between some types were small, but testing and examination of enemy aircraft helped to develop tactics that would exploit the relative weaknesses of an enemy type whilst exploiting your strengths.
Cheers
Steve

 

[Shortround6]

I don't too excited about differences until they get into high single digits, like over 5% and even then take them with a grain of salt.
I believe, but could be wrong, that many contracts had an allowable margin or performance, for some reason 3% springs to mind for the US contracts. Some contracts spelled out penalties, like XX dollars for every MPH under the allowable tolerance a plane tested in acceptance testing. There was a limit though, too slow and the plane was rejected and had to be reworked to bring it up to standard.
Some memoirs say how the pilot in question flew a number of different replacement aircraft and picked ONE to be his normal aircraft Usually already an ace or squadron commander RHIP
Good crew chiefs were also prized more than a faithful wife.
I would hazard a guess that national test facilities also had experienced mechanics/fitters and NOT the ones that graduated last week in the bottom 1/2 of their class.
The most common part to cause problems in testing were probably spark plugs (open to correction) but then they might be the most common spare part available to the country doing the testing. The English might be able to scrounge spark plugs from a number of wrecks. Spare props being much harder to come by.

 

[GrauGeist]

A good example of resurrecting a wrecked enemy plane and getting it airworthy for testing, would be the Alaskan Zero.

I'm sure that the English countryside provided a wealth of spare parts for testing various Bf109s, Bf110s and the like...but the effort they went to in rebuilding that Zero was impressive.

 

[pbehn]

A good example of resurrecting a wrecked enemy plane and getting it airworthy for testing, would be the Alaskan Zero.

I'm sure that the English countryside provided a wealth of spare parts for testing various Bf109s, Bf110s and the like...but the effort they went to in rebuilding that Zero was impressive.

The Fw 190 was a problem but happily someone mistook the UK for France and landed one in perfect condition.

 

[Shortround6]

I said that such tests are not definitive because there are many variables, not least a test pilot who would be relatively unfamiliar with the enemy machine. Nonetheless the data obtained is valid and it was used to develop fighting tactics for use against the various enemy types.

Cheers

Steve

Aw, I did like shooter's contention that the pilots at Farnborough didn't push the 109 in turns because they were unfamiliar with slats and afraid of them. Handley Page was the co-holder of the patent and stuck them on practically everything the company made, including the first 50 Halifax's. Even Swordfish had slats on the upper wing (in front of the ailerons, lower wing didn't have ailerons). Test pilots at Farnborough were hardly strangers to slats either in theory or practice.
Breaking the only flying example of the 109 in England may have introduced a bit of caution in general.

 

[stona]

The trials of Armin Faber's Fw 190 gave the British much needed insight into what they already knew to be a formidable fighter.

Eric Brown:

"The AFDU trials confirmed what the RAF already knew - that the Fw 190 was a truly outstanding combat aircraft. They also produced vitally important information which went some way towards restoring the situation in so far as the RAF was concerned and in eradicating something of the awe in which the Focke-Wulf had come to be held by Allied pilots. It was concluded that the Fw 190 pilot trying to "mix it" with a Spitfire in the classic fashion of steep turning was doomed, for at any speed -even below the German fighter's stalling speed- it would be out-turned by its British opponent . Of course the Luftwaffe was aware of this fact and a somewhat odd style of dogfighting evolved in which the Fw 190 pilots endeavoured to keep on the vertical plane by zooms and dives, while their Spitfire-mounted antagonists tried everything in the book to draw them on to the horizontal. If the German pilot lost his head and failed to resist the temptation to try a horizontal pursuit curve on a Spitfire, as likely as not, before he could recover the speed lost in a steep turn he would find another Spitfire turning inside him! On the other hand, the German pilot who kept zooming up and down was usually the recipient of only difficult deflection shots of more than 30 deg. The Fw 190 had tremendous initial acceleration in a dive but it was extremely vulnerable during a pull-out, recovery having to be quite progressive with care not to kill the speed by 'sinking' "

And:

"The AFDU comparisons between the Focke-Wulf and the Spitfire Mk IX - with the former's BMW 801 at 2,700 rpm and 20.8 lb (1.42 atas) boost and the latter's Merlin 61 at 3000 rpm and 15lb (1.00 ata)- has revealed that the German fighter was 7-8mph (11-13km/h) faster than its British counterpart at 2,000 ft (610 m) but that the speeds of the two fighters were virtually the same at 5,000 ft (1525 m). Above this altitude, the Spitfire began to display a marginal superiority, being about 8mph (13km/h) faster at 8,000 ft (2440 m) and 5 mph (8km/h) faster at 15,000 ft (4570 m). The pendulum then swung once more in favour of the Focke-Wulf which proved itself some 3 mph (5km/h) faster at 18,000 ft (5485m), the two fighters level pegging once more at 21,000 ft (6400 m) and the Spitfire then taking the lead until at 25,000 ft (7620 m) it showed a 5-7 mph (8-11 km/h) superiority.
In climbing little difference was found between the Fw 190 and the Spitfire MkIX up to 23,000 ft (7010 m), above which altitude the German fighter began to fall off and the difference between the two aircraft widened rapidly. From high-speed cruise, a pull-up into a climb gave the Fw190 an initial advantage owing to its superior acceleration and the superiority of the German fighter was even more noticeable when both aircraft were pulled up into a zoom climb from a dive. In the dive the Fw190 could leave the Spitfire Mk IX without difficulty and there was no gainsaying that in so far as manoeuvrablity was concerned, the German fighter was markedly superior in all save the tight turn – the Spitfire could not follow in aileron turns and reversals at high speed and the worst height for its pilots to engage the Fw 190 in combat were between 18,000 and 22,000 ft (5485 and 6705m), and at altitudes below 3,000 ft (915m).
The stalling speed of the Fw 190A-4 in clean configuration was 127 mph (204 km/h) and the stall came suddenly and virtually without warning, the port wing dropping so violently that the aircraft almost inverted itself. In fact, if the German fighter was pulled into a g stall in a right turn, it would flick out into the opposite bank and an incipient spin was the inevitable outcome if the pilot did not have its wits about him.
The stall in landing was quite different, there being intense pre-stall buffeting before the starboard wing dropped comparatively gently at 102 mph (164 km/h)"

Cheers

Steve

 

[pbehn]

Aw, I did like shooter's contention that the pilots at Farnborough didn't push the 109 in turns because they were unfamiliar with slats and afraid of them.

That made me smile too, all the test pilots reports I have read discuss the stall characteristics and how easily the plane recovers. Test pilots spent a large part of their time stalling aircraft the idea that a test pilot would be scared of an aircraft is a bit strange unless of course the plane just wouldnt recover.

 

[stona]

the idea that a test pilot would be scared of an aircraft is a bit strange unless of course the plane just wouldnt recover.

There would only be one way to find out.....that's what parachutes are for

Cheers

Steve

 

[GrauGeist]

Aw, I did like shooter's contention that the pilots at Farnborough didn't push the 109 in turns because they were unfamiliar with slats and afraid of them. Handley Page was the co-holder of the patent and stuck them on practically everything the company made, including the first 50 Halifax's. Even Swordfish had slats on the upper wing (in front of the ailerons, lower wing didn't have ailerons). Test pilots at Farnborough were hardly strangers to slats either in theory or practice.
Breaking the only flying example of the 109 in England may have introduced a bit of caution in general.

I agree..that did bring a smile to my face as well!

Perhaps that's why the F-86 was having so much difficulty with those pesky MiGs in Korea early on...but once the F-86 pilots got over their fear of slats, the MiGs were in trouble!!

 

[rochie]

And maybe thats why the Spitfire was re hashed WWI technology as it didnt have slats ?

 

[GrauGeist]

And maybe thats why the Spitfire was re hashed WWI technology as it didnt have slats ?

In all fairness, perhaps he mistook the Hurricane slip-wing for the Spitfire...it sort of looks WWI-ish...

From a distance...

After several beers...

It's an honest mistake, really!

 

[Shortround6]

Yep, the British should have persevered with this design instead.

At least it had slats.
Or for a bomber prototype

Or fit heavy nose guns to this as a bomber destroyer. Just think of the angle of attack this could pull