Welcome and thanks for clearing a few things up. It is a pity that Mr.Davies book has not been written with that level of details you showed in those few sentences here. I`m really enjoying reading you. English is a great language, wish all people on this planet have learnt it in the past, we would have been discussing things much easier. I regret that I can not bring my older colleagues (Flogger pilots) over here as they do not read and write a word in English. You asking why? Well, we learnt only one foreign language for the most part of our lives, guess which one.. Some of the Flogger pilots I know retired in nineties with roughly several hundred flight hours more in the cockpit than you, some continued and retrained for another type like the Su-25 or ended careers in the military flight school on the L-39 jet trainers. Please do not be angry with me when I doubted "Red Eagles" experience with the Flogger recently, but that`s what I thought about Mr. Davies book and his endless bitching and giving readers a wrong impression of what you remember when you`ve been flying it. Well, if that is your experience, no one can change that....In general I feel nothing but admiration for Red Eagles, all military pilots, no matter what side they have flown for, bcs once when I was a little boy ( I`m not alone here) I have dreamed to be one as well. Nevermind, I`m working for years in the aircraft MRO service once overhauling the Migs-23BN/UB, currently me being assigned to the type Mig-29.
That`s an unique experience pointing to a serious engine design fault. I wonder whether the designer/test pilots would have confirmed this finding that engines installed in the Mig-23M, MS, MF were about to be destroyed in an aircraft spin. Do you remember what facts led you to believe the R29-300 engine was not braced to engine casing sufficiently when experiencing lateral Gs or by any chance is there a possibility that you might be mistaken in that conclusion?
Originally Posted by Bandit 42
From engine design standpoint, beginning with engine to fuselage attachments, engine casing and suspension system, type of bearings, rotor and stator assembly of the eleven stage twin-spool compressor and turbine section, front and rear engine supporting struts,........ the engine R29-300 used with the Mig-23M, MS, MF is almost identical to the R29B-300 used with the BN. The difference between them, the R29B-300 is having a slighty smaller combustion chamber and shortened nozzle optimalized (no laval type, supersonic converging/diverging nozzle) for subsonic regimes and low altitudes only. All what it meant was less thrust but a bit better SFC value. There were also changes to the engine fuel-regulation system, but by any means the R29B-300 can`t be seen as an improved version of the R29-300, but rather, a modification to suit subsonic operations of the Mig-23BN.
I`m not trying to underestimate the situation during the spin, but would like to point out the importance of another reason that may explain the damage of the R29-300 engine in your case. When entering a spin the R29-300 engine (most of) is going to stall very hard as a result of disrupted air flow to the air intakes and engine power settings. You may remember hearing an extremely loud pulsating noise and bangs like swiping metal on metal.
This was not the sign of engine hitting the side of the case or compressor/turbine blades snaping each other, but the sound of inlet duct panels and auxialiary louvers deforming caused by high vibrations and pressure unbalance inside the intake/engine section. Flogger pilots whether unintentionally or intentionally entering spin with arising compressor surge were instructed to immediately shut down the engine to reduce risk of burning/destroying turbine blades caused by engine overheating (red warning light). The turbine outlet temp gauge "TOT" gauge ITG-1(placed next to Fuel meter) might get crazy within several seconds bcs the turbine blade cooling was insufficient, not to mention fuel still flowing, even worse if burning. The point I want to make here is that the compressor surge was a very common phenomenon for pilots with the Mig-23/R29-300 and we lost a plane that way as well, overheating engine not able to restart, at low altitude, but pilot ejected safely. I remember to read in the past aviation history that a compressor surge might be able to completely destroy an engine (blades snaping each other due to violent vibrations), but we doubt the R29-300 was that case, not to mention the engine being damaged by an aircraft spin movements.....for sure most unlikely.
The problem with the Mig-23 suddenly departing from controlled flight and entering spin at high AOA with less warning has been known from the begining. When flown at high AOA and not carefully watching your yaw rate the Mig-23 could enter spin at considerably lower AOA compared to initially evaluated 35-36 degrees. This issue has been addressed in east block Air forces during late seventies on all previously delivered Floggers (except the Mi-23BN) by installing a cross-coupling system between the rudder and lateral control channel of the Mig-23. The DPR-23 (btw. Mig-29 is using the same) probe "Datchik Polozhenja Ruchky" was attached to the control column sensing its lateral movements. According to airspeed, altitude, lateral stick movements and the actual AOA the SAU-23 autopilot was adjusting the rudder to counteract unwanted yaw motions when turning on high AOA ensuring better directional stability. You know the system probably under another name, e.g. ARI - Aileron Rudder Interconnect. I wonder if anyone of Red Eagles has test flown F-14 Tomcat, aircraft badly known to be prone to spin and compressor surge. Why wasn`t this system installed on the Mig-23BN? It is obvious, because the BN hasn’t been designed for the high AOA air-to-air missions even if the "duckbill" shaped nose was making the situation even worse. Meaning the asymmetrical flow pertubations around aircraft forebody creating yawing moments. By the way, there are numerous memoirs written by former Mig test pilots or better say "spin doctors" like S.A. Mikoyan, A.V. Fedotov, V.A. Orlov, A.A. Scherbakov or V.E. Menitskyj evaluating the Flogger for the most part of their lives confirming your findings about spin characteristics of the Mig-23.
If I understood it correctly, some of you have flown both the Mig-21 and the Mig-23 together. The chapter describing Red Eagles experience with Mig-23 landing characteristics was the most terrifying one. Actually, true is that during the landing with the Flogger, pilot should have paid more attention to both the airspeed and AOA in relation to landing weight before touching the runway, bcs when a little surplus of speed or improper AOA was set you bounced back into the air or ending up on the runway jumping like a crazy goat. All it required was a bit more practicing with the Flogger high-lift landing configuration. No one was complaining, but hell are you saying the landing with the Mig-21 was ever better at 170-180knots? Not sure you were flying the Fishbed version with the blowing flap system. Anyway, have you ever noticed that Flogger main landing gear was extended a bit asymmetrically causing negligible yawing effect you`re complaning about when landing? Thanks
Last edited by martinez; 27th July 2009 at 20:36.
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