mark.bitterlich(at)navy.m
Guest
|
 Posted: Mon Jun 10, 2013 10:43 am Post subject: New Subject: Landing Gear Operation on a YAK-50 (LONG) |
 |
|
Doc LONG answer,
Shortly after I purchased my YAK-50 over 13 years ago, I had the chevron
seals in one actuator fail. Without help from the YAK List (not sure it
even existed back then), and without help from any manuals, I
disassembled that whole mess and step by step figured out how it all
worked. Landing gear legs laying on the hangar floor, actuators taking
apart on work benches, landing gear selector valve removed and taken
apart. Every single piece examined bit by bit, every air line traced
out from source to destination. I wrote a few articles covering that
experience, and some of them were "copied" and made into much better
presentations. From all this, I learned how the landing gear system
worked, including just how important those up-lock springs are!
I'm just saying it was not luck that allowed me to ferry that YAK-50
across the country with a known air leak problem, it was knowledge and
experience on how the system worked that allowed me to apply a technique
properly to achieve a desired solution. This is the knowledge I am
trying to pass on via this topic of conversation.
One of the problems with the YAK-50 is that the green "Down and Locked"
Landing Gear Indicator lights can easily be behind your knee if you are
relatively tall in stature. In other words, you have to consciously
move your leg to look at both of them. It dawns on me that it might be a
smart idea to move them up into your direct line of sight! You
mentioned hearing the gear, and that it sounded normal. This is an easy
habit to get into.... since I have done the exact same thing, and it's a
BAD habit (IMHO). Since some history with one gear being down and not
locked, I will never EVER again fail to FOCUS on BOTH of those darn
lights! Needless to say, I doubt you will either.
I am sure you placed the landing gear handle down. I am sure there was
enough air in the system to release both gear legs from the up-locks and
start them on their way down. At some point in that process, the air
ran out.. for whatever reason..... or was not flowing with enough volume
to force the gear forward into the air-stream to where the mechanical
down-locks would then engage. The gear down and lock lights were
probably not illuminated. You landed, the gear was not locked and back
up they both went.
I might as well tell a similar story of woe, since it will reinforce the
lesson that you have offered. In this case, an A&P/AI mechanic felt
that the left gear leg had too much lateral play. He tightened the
attach bolt to take out the play. Shims were suggested. he said B/S to
that, and that the nut just needed to be tightened. Well, the gear
swung perfectly in the hangar when tested. "See?" he says.
On the first flight following the Conditional, on a wheel landing, the
left gear collapsed, the aircraft wing came down mighty close to the
runway and the aircraft veered to the left. Full power, jammed right
rudder and it goes airborne again. In the pattern, the right green down
and locked light was on. The left one was not. Emergency air was
applied and the left green down and locked light came on. After landing
safely, it was noticed that about 4-6 inches had been ground off each
end of the prop. It had flown around the pattern like that. The tower
was called and told of possible FOD on the active. The security truck
went out and collected a sandwich bag full of very small splinters of
painted wood, with the comment: "This is all we could find".
End of story: Following a complete inspection of the engine,
readjustment of the landing gear attach bolt nut to where it was before,
and the aircraft has since flown 300 hours since without incident.
As regards your prop strike.... I am sure you have read what people far
more expert than myself have said about it, but I will say that you've
got a pretty good expert close to you in the form of Dennis Savarese.
That said: Make sure you very carefully and very exactly check the
timing on the mags. Not to each other, but to the timing they should
be, using the piston position, safety wire to dial method. If the
timing is off *AT ALL*, then the accessory shaft has twisted and you are
looking at a mandatory tear down. If the engine timing is OK, I would
be tempted to have the planetary gear box inspected and if that checks
good then I would be inclined to light her off and check her out.
Others may not agree, and I have no dog in this fight per se. Only the
person that was there when it happened can make a true and honest
evaluation of how bad it really was. I don't have a clue why oil is
seeping from your carb throat. Someone else needs to discuss that one!
I am not a hydraulic line expert... but I am not totally ignorant of
them either. I would not replace all lines with braided Aeroquip (not
sure if that was what you were suggesting or not). If you are going to
re-plumb the aircraft, use rigid lines where rigid lines originally
were, and flexible lines, where flexible lines originally were. The
aluminum lines used on the YAK's are very VERY pure aluminum (I've had
them tested), but that also means they are rather soft as compared to
what is typically used in the West. Be careful of changing the design
of any air line that "moves". Putting in braided Aeroquip puts
additional load on fittings they attach to, if that line "moves" during
intended operation. So you could end up "fixing" the line, and then
snapping off a fitting.
It is wise to approach "re-design" very carefully. For example, I would
guess most everyone would think that the engine cooling shutters are
there to control airflow over the engine. They are, and that's true...
but they *ALSO* provide mounting strength and stability to the front of
the upper and lower engine cowls. A good thing to know if you are
tempted to replace the original shutter design with a Sukhoi type IRIS.
Good luck Doc, I my heart goes out to you and I hope the rebuild is not
too bad.
Mark
--
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
