portman Posted January 19, 2015 Posted January 19, 2015 (edited) Hi there, it's common practice to flip the gear handle back to the neutral position after taking off. The manual says this is to avoid bleeding of compressed air used for braking the wheels when the gear is being retracted. Well, a quite popular german book about the MiG-21bis, written by a former GDR MiG mechanic, says that the wheels where stopped hydraulically, and no compressed air was used for this. Therefore you don't need to flip back the handle just to save compressed air. The true reason for flipping the gear handle back to neutral is the following: The LG is being operated hydraulically, while compressed air is used for emergency LG extension. Hydraulic pressure is much higher than air pressure, so if you don't flip the gear handle back to neutral, the hydraulic pressure is "pushing" the LG back into the wheel well all the time - so if you try to use the emergency gear handle, the compressed air has not enough "power" to extend the LG. Can anyone confirm this? Leathernecks? :music_whistling: (sorry for my english, it's been a busy day) Edited January 19, 2015 by portman Mancher zum Meister sich erklärt, dem nie das Handwerk ward gelehrt!
Flagrum Posted January 19, 2015 Posted January 19, 2015 Interesting. Which book is it that you are referring to?
portman Posted January 19, 2015 Author Posted January 19, 2015 Interesting. Which book is it that you are referring to? The book is called "MiG-21" :) and it's written by Holger Mueller. Mancher zum Meister sich erklärt, dem nie das Handwerk ward gelehrt!
Dolphin887 Posted January 19, 2015 Posted January 19, 2015 Compressed air is used if the handle is in upward position and the rudder pedals are moving. This is because the compressed air is used to brake the gears during the retraction process, without pilot's control. As for the emergency extraction, you statement is true. It is mentioned in emergency gears extraction procedure (handle have to be in the neutral position). Note that you would like to extract the gears using the emergency procedure only when the hydro pressure is actually lower than the air pressure (in wast majority of cases). Since the emergency extraction is extremely rare procedure, main reason for placing the gear handle in the neutral position is air-waste. I meet with Mr. Mueller. Some of the images on his Internet site (and most likely in the book) are taken in Serbia during his visit. He was a mechanic on MiG-21 relatively short time in Eastern Germany. Power through superb knowledge, training and teamwork. [sIGPIC][/sIGPIC]
Art-J Posted January 19, 2015 Posted January 19, 2015 Thanks Dolphin. I think this topic comes up every now and then because of the manual You guys prepared for the MiG. On page 67 it says the wheels are stopped during retraction by hydraulic installation, while page 69 says they're stopped by pneumatic installation. That makes readers a bit confused obviously. Could we settle for good which version is correct :D ? i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.
Dolphin887 Posted January 20, 2015 Posted January 20, 2015 Both is true: hydraulic is used to operate air pressure valve. Power through superb knowledge, training and teamwork. [sIGPIC][/sIGPIC]
Art-J Posted January 20, 2015 Posted January 20, 2015 Roger that! Would You mind sparing a few minutes to comment on ASP-PFD "auto" mode in the gunsight-related thread as well? It seems that some folks are confused about fixed 300 m setting, this issue comes up in different threads every few weeks, Your comment might clear things up for good. i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.
Flagrum Posted January 21, 2015 Posted January 21, 2015 The book is called "MiG-21" :) and it's written by Holger Mueller. Could not resist - bought it and today it arrived! :o)
Recommended Posts