=475FG= Dawger Posted May 18 Posted May 18 20 hours ago, Dragon1-1 said: In most jets, you just have to keep your feet on the floor. For normal (1 G) maneuver this is kinda sorta true but not really. The yaw displacement isn't very noticeable but it is still happening It isn't true at all when maneuvering above 1 G acceleration. 20 hours ago, Dragon1-1 said: Your goal is to be wings level when you pickle, so no rudder input should be needed. Wings level at the pickle may or may not mean ailerons/spoilerons neutral. If they aren't in trail, there will be yaw displacement requiring rudder correction.
TotenDead Posted May 25 Posted May 25 I have a question that's somewhat related to bfm performance of the phantom. At what angle of Attack does a slatted phantom stall? Just for example, here's the graph for the pre-slatted version, you can see that the aircraft stalls at around 23 degrees of aoa. Спойлер So, slats should've improved the alpha capability of the aircraft. But how much? As far as I know, manuals use "units" which is, eh, super helpful. Perhaps someone knows numbers in some proper measurements? 1
Super Grover Posted May 26 Posted May 26 (edited) Sadly, there's no simple answer to this. First of all, with all the information I have, I wouldn't call the linked picture a reliable source. Then, the question is what alpha are you interested in - is it wing or fuselage (different F-4 sources use different references for that)? Then there's that constant issue of the conversion between the AoA in units and degrees - and this is probably the most challenging question we had to answer to properly use the resources when working on the FM of the F-4E. Finally, there are very significant differences between wind tunnel data and flight tests, and the in-flight calibration of the production AoA measurements was probably one of the issues. Finally, the problem is the definition of the stall point and how the stall is approached, which significantly impacts how the aircraft behaves. It was easier to test and collect the point when the aircraft departed. Back for a moment to the attached plot - according to McDonnell, 1G departures for the base wing F-4E could happen as low as at 19° of wing AoA - so lower than what is presented in that graphics. And after this too long introduction , when I drew all the uncertainties and how one should take all those numbers with a grain of salt, I can write that the slatted wing stalls/departs around 3°+ later than the non-slatted wing. Edited May 26 by Super Grover 1 Krzysztof Sobczak Heatblur Simulations https://www.facebook.com/heatblur/
TotenDead Posted May 29 Posted May 29 В 27.05.2025 в 01:23, Super Grover сказал: Sadly, there's no simple answer to this. First of all, with all the information I have, I wouldn't call the linked picture a reliable source. Then, the question is what alpha are you interested in - is it wing or fuselage (different F-4 sources use different references for that)? Then there's that constant issue of the conversion between the AoA in units and degrees - and this is probably the most challenging question we had to answer to properly use the resources when working on the FM of the F-4E. Finally, there are very significant differences between wind tunnel data and flight tests, and the in-flight calibration of the production AoA measurements was probably one of the issues. Finally, the problem is the definition of the stall point and how the stall is approached, which significantly impacts how the aircraft behaves. It was easier to test and collect the point when the aircraft departed. Back for a moment to the attached plot - according to McDonnell, 1G departures for the base wing F-4E could happen as low as at 19° of wing AoA - so lower than what is presented in that graphics. And after this too long introduction , when I drew all the uncertainties and how one should take all those numbers with a grain of salt, I can write that the slatted wing stalls/departs around 3°+ later than the non-slatted wing. Thank you for the info! The picture I used is from this document Спойлер null Also attached it to the post just in case The analysis is generally focused on the F-4J, however: Спойлер null Hopefully, the paper will be useful When it comes to the AOA, it would be interesting to see some true AoA numbers, I'd assume that there should be a formula to recalculate local aoa (or even units) to the true one. Just as an example - a formula for local-to-true aoa recalculation from MiG-23ML FM Спойлер Speaking of 19 degrees departures, perhaps those happened when a pilot missed to see that the aircraft is flying with some degree of yaw? The 3 degrees difference between hard and slatted wings is an interesting piece of information. It would be great if the hard wing version aoa could be determined at least for some best case scenario a101646 (1).pdf
Recommended Posts