Crump Posted April 3, 2014 Author Posted April 3, 2014 you provide the test aircraft as a base of evidence for the behaviour of front line machines and that is not selective? Well, the test aircraft was designed to safely explore the absolute limits of the design and beyond. It was good enough for the engineering firm that designed the aircraft and the customer who operated the aircraft to fulfill their contract. 1
DD_bongodriver Posted April 3, 2014 Posted April 3, 2014 Precisely, therefore not representative of the production front line aircraft which were plagued with the problems it was designed to explore. 2
Crump Posted April 4, 2014 Author Posted April 4, 2014 Precisely, therefore not representative of the production front line aircraft which were plagued with the problems it was designed to explore. Again, The engineers and the Luftwaffe would disagree with you. I do too. 1
DD_bongodriver Posted April 4, 2014 Posted April 4, 2014 You don't speak for the Luftwaffe or engineers, and your disagreement is simply par for the course.
Crump Posted April 4, 2014 Author Posted April 4, 2014 The issue occurs when pilots exceed the published operating limitations just as any design. 1
DD_bongodriver Posted April 4, 2014 Posted April 4, 2014 Yes, obviously failures can be expected when exceeding limits, the interesting thing to note is that this document is calling for a reduction in speed, an assumption on limits being exceeded but a lack of confidence that the limitations are sufficient.
Crump Posted April 4, 2014 Author Posted April 4, 2014 lack of confidence that the limitations are sufficient. It was extremely rare that anyone from any nation did high speed trials. It was extremely dangerous the limitations were set by standards which did not include test flight to the limits because crossing them was catastrophic. The pilot that conducted the high speed trials for Mtt was paid extremely well for his risk. For Vne, it was generally calculated for both dynamic pressure effects and mach effects. Mach effects were previously unknown or at least never experienced until the beginning of the war. The Germans were very much surprised by the behaviors of the FW-190 at high speeds just as the Americans were surprised at the deaths caused by the P-38 compressibility issues. The previous limitation for the Bf-109 was a generic 750kph Indicated Airspeed. Keep in mind that it was in November of 1941 the United States aeronautical engineering community was introduced to mach effects when test pilot Ralph Virden lost his life in the XP-38 dives. Development of High Speed flight.pdf 2
DD_bongodriver Posted April 4, 2014 Posted April 4, 2014 You miss the point entirely, this document is calling for the fleet wide imposition of stricter limitations, that does suggest a lack of confidence in the basic machine, nothing to do with nervous test pilots.
Crump Posted April 4, 2014 Author Posted April 4, 2014 (edited) You miss the point entirely No I understand your point, it is just wrong. The "lack of confidence in the basic machine" is just not valid. Edited April 4, 2014 by Crump
Crump Posted April 4, 2014 Author Posted April 4, 2014 The directional instability manifested as a Dutch roll exhibited by the Bf-109 defined the mach limits of the design. It is the limit of the envelope and not the normal operating range. It is not a valid as a "stability and control" problem because it does not occur in the normal operating envelope of the design.
AndyJWest Posted April 4, 2014 Posted April 4, 2014 If there are "stability and control" problems at the limit of the envelope, the envelope needs adjusting. As the Luftwaffe concluded... 1
DD_bongodriver Posted April 4, 2014 Posted April 4, 2014 No I understand your point, it is just wrong. The "lack of confidence in the basic machine" is just not valid. Please at least attempt to bring a cogent argument instead of simple contradiction.
Kurfurst Posted April 4, 2014 Posted April 4, 2014 Well no actually, the opening statement of Crumps test report clearly states it had insufficient elevator authority at high mach number, a condition backed up by a vast amount of combat reports and pilot opinions. Definie insufficent. The 1943 Lukas dive trials with the 109F confirm that the aircraft can be recovered by the stick alone from a 70-80 degree dive at full power and near Vne within 1100 meter altitude, at about 850 kph TAS. That's hardly unrecoverable, and is valid for the most extreme dive conditions possible.You may wish to calculate the g-forces pulled. Crumpp trials with 190A and 109G show that the 190 has lighter elevator forces to start with, but the 109s elevators are much less effected by Mach number (ie. stick forces do not rise so sharply as on the 190), a condition that is probably rooted in the thinner airfoil of the 109 horizontal stabilizer. Furthermore, British trials of 109F confirm the same: "During the descent, pressure was built up higher than it had ever been during the trip, and the aircraft was dived at 420 indicated and the aileron control still found to be quite good, though considerably heavier. Elevators quite good but not very light." and "Manoeuvrability 7. No manoeuvrability trials were carried out against other aircraft but the Me.109F was dived up to 420 m.p.h., I.A.S., with controls trimmed for level flight and it was found that altough the elevators had become heavy and the ailerons had stiffened up appreciably, fairly tight turns were still possible. It is considered, however, that the aircraft could have been out-turned easily by a Spitfire. At high speed the ailerons are more effective than the fabric ailerons of the Spitfire, but are not as good as the metal ones. As a result of the heaviness of the elevators at speeds over 400 m.p.h., violent evasion is not possible, and the aircraft would present a simple target to a following Spitfire. Similarly, a Spitfire attacked by a Me.109F from above, should have no difficulty in evading if he turns sharply towards the direction of the attack. It is considered that recovery from a high speed dive near the ground would be difficult, as the loss of height entailed is considerable. This may accountfor occasional reports of Me.109F's being seen to dive straight into the ground without appearantly being fired at." Again, pulling "fairly tight turns" at 420 mph IAS can be hardly equated with insufficient elevator authority. Of course Spitfire can perform far more violent pull-ups, to the extent that the airframe can break up to overload. That's hardly preferable and hardly surprising, given that the Spitfire's elevator controls were on the extreme light side for all WW2 fighters, and on the plus side that aircraft displayed longitudal instability and tended to tighten up turns. All these characteristics combined presented a very real danger to its own pilots during tight pull-outs, as the pilot could very easily pull so much g to exceed the 10-12 g absolute break limit of the airframe and make it shred it wings, as it happened quite often and was a real concern to the RAF, as testified by numerous tests, the Spitfire's own pilots manual and various trials. The plus side was that an experienced Spitfire pilot with a hand for the delicate stick could perform tight turns and change direction sharply. The 109 control was more suited for the avarage or inexperienced pilot, as he was unlikely to overstress and break or overcontrol and stall the aircraft. The relative control characteristics of the aircraft explain this difference well. The 109 had a elevator stick force of about 20 lbs / g, ie. on the heavy side, and high longitudinal stability and well balanced controls, the Spitfire merely a stick force of merely 4 lbs / g, i.e. extremely light, with extremely unbalanced controls with excessively heavy ailerons requiring the pilot to arm wrestle them, while touching the elevator with a light fingertip. Such an assymetric and badly harmonized control setup was deemed unacceptable in both the USA and in Germany. Messerschmitt could of course alter the control setup, and made such trials, but in the end the very specific reason why the chief Messerschmitt pilot rejected the lighter elevators with reduced travel was that it would result in bad control harmony. 1
DD_bongodriver Posted April 4, 2014 Posted April 4, 2014 Definie insufficent. https://www.google.co.uk/#q=insufficient Cause: 1. Explanation of accidents in the front-line units. (Over-compensation of the aileron controls and insufficient elevator authority at high mach numbers). "Manoeuvrability 7. No manoeuvrability trials were carried out against other aircraft but the Me.109F was dived up to 420 m.p.h., I.A.S., with controls trimmed for level flight and it was found that altough the elevators had become heavy and the ailerons had stiffened up appreciably, fairly tight turns were still possible. It is considered, however, that the aircraft could have been out-turned easily by a Spitfire. At high speed the ailerons are more effective than the fabric ailerons of the Spitfire, but are not as good as the metal ones. As a result of the heaviness of the elevators at speeds over 400 m.p.h., violent evasion is not possible, and the aircraft would present a simple target to a following Spitfire. Similarly, a Spitfire attacked by a Me.109F from above, should have no difficulty in evading if he turns sharply towards the direction of the attack. It is considered that recovery from a high speed dive near the ground would be difficult, as the loss of height entailed is considerable. This may accountfor occasional reports of Me.109F's being seen to dive straight into the ground without appearantly being fired at." Again, pulling "fairly tight turns" at 420 mph IAS can be hardly equated with insufficient elevator authority. Of course Spitfire can perform far more violent pull-ups, to the extent that the airframe can break up to overload Though interestingly there is not much evidence that Spitfires had problematic break-ups like the 109 clearly did, this would suggest that the effectiveness of the Spitfires elevator presented no real problem to the pilots and the Spitfire airframe was generally stronger, but we digress, the Spitfire is not relevant to this forum and therefore renders your chronic agenda redundant.
Kurfurst Posted April 4, 2014 Posted April 4, 2014 (edited) Though interestingly there is not much evidence that Spitfires had problematic break-ups like the 109 clearly did, this would suggest that the effectiveness of the Spitfires elevator presented no real problem to the pilots and the Spitfire airframe was generally stronger, but we digress, the Spitfire is not relevant to this forum and therefore renders your chronic agenda redundant. Wrong on all accounts I am afraid, as the Spitfire's dive and control, wing twisting, bending and breaking issues are well documented in its very own manual, RAE, Rechlin's and NACA's trials and the various literature, there are similar warnings against the use of ailerons in dive etc. etc. If you're in partisan denial of this - well its fine with me and let's drop that subject, I merely brought up as a counter example of the effects and downside of different (opposite) control characteristics and the reasoning behind. Let's go back to defining insufficient elevator authority at high Mach numbers, which is your chronic, baseless agenda and in contrast with the very findings of 1944 190/109 Mtt trial posted above by Crumpp. It may well be that during the 1943 dive trials they have suspected some kind of Mach influence on the elevator, but the 1944 dive trials fly in your face in that regard and clear up the case that the 109G had no Mach related elevator issues. Now then 1. Define what you consider "sufficient" elevator authority. 2. Calculate the g-load pulled in the Lukas dive tests Edited April 4, 2014 by VO101Kurfurst 1
DD_bongodriver Posted April 4, 2014 Posted April 4, 2014 Now then 1. Define what you consider "sufficient" elevator authority. I don't need to, you must find out what the Luftwaffe and Mtt considered 'insuficient' when they wrote it in a report concerning stability and control problems of the 109. 2. Calculate the g-load pulled in the Lukas dive tests Pay me.
Kurfurst Posted April 4, 2014 Posted April 4, 2014 I think at this point its quite obvious that you are just trolling the thread without the slightest intention (and perhaps, capacity) to add anything of substance to it. Please leave then and find some other playground. 1
FlatSpinMan Posted April 4, 2014 Posted April 4, 2014 Okay. Had several complaints about this thread, all from actual participants who report unreasonable or unhelpful behaviour in others, all the while seemingly unable to recognise the same behaviour in themselves. I have no interest in your repeated and persistent inability to get along and discuss things in a reasonable manner. We've been letting it roll a bit but it is just hopeless. This thread is over. Some other mod may disagree, but I personally am inclined to lock any similar thread immediately to save needless aggravation.
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