Do you Brits even perform maintenance work in high viz jackets? Do you have high viz pyjamas in bed?
Two times I have not flown an aircraft for three months – and both times several things were broken after that period. while I never had engine problems (except a new cylinder after 20 years on a 320) … i am SURE that Flying is a good way to keep aircraft in good shape, especially: o-rings, batteries, brakes, seals, fuel systems, pumps and electrics.
And my aircraft were always hangared.
Do you Brits even perform maintenance work in high viz jackets? Do you have high viz pyjamas in bed?
Think it’s the only jackets they can afford !!- wearing them because the hangar temperature is sub zero.
Given up on pyjamas, high performance duvet instead !
Ah, #103 has rectified itself – maybe editor intervention.
Yes, I fixed it up. See Posting Tips
A quote has to be a distinct paragraph i.e. a blank line above (or be at the start of a post) and a blank line below. To some extent the quote button fixes this up but not completely.
It would be great to hear the details of what you found in your engine, Warley Air. If you have any difficulty uploading pics etc, just email them to me and I will sort it.
Regarding your landing gear issue, I don’t know what that could be. There could be air in the system, which when compressed, gives a little. Has the system been bled properly? I know the fairly common UK practice is to not change any fluids except engine oil, for 20-30 years! Otherwise, these systems contain only one hydraulic circuit, and the fluid takes the path of least resistance, so if e.g. your LH main gear is marginally more sticky than the RH main gear, the RH gear will move first, until the geometry of the hydraulic actuators evens it out and then the LH gear will move, etc. The nose gear might move first, or last. and at the very end (the very top) of the travel, the resistance is so high (because the three gear components are compressing hard rubber bungs) that all kinds of little movements may be seen. See this Your engineer probably never checked how freely the gear moves by hand; it’s a tricky process which involves either dismantling the locks, or using the hydraulics to just-unlock the gear and then you can move it by hand.
Why on the video below does the ‘mains’ fully retract and then drop somewhat before completing the cycle ?
Engineer did not seem particulary concerned about what looked like a ‘hiccup’ to me.
It is a very simple system where the resistance causes difference. It is normal operation for these kind of gear, see also Peter´s gear topic.
Regarding your landing gear issue, I don’t know what that could be. There could be air in the system, which when compressed, gives a little. Has the system been bled properly? I know the fairly common UK practice is to not change any fluids except engine oil, for 20-30 years!
I would be really amazed if UK companies would be really THAT bad. I can not imagine that to be honest.
Otherwise, these systems contain only one hydraulic circuit, and the fluid takes the path of least resistance, so if e.g. your LH main gear is marginally more sticky than the RH main gear, the RH gear will move first, until the geometry of the hydraulic actuators evens it out and then the LH gear will move, etc. The nose gear might move first, or last. and at the very end (the very top) of the travel, the resistance is so high (because the three gear components are compressing hard rubber bungs) that all kinds of little movements may be seen.
It is all about resistance, it won´t be compressing the rubber parts yet at that video clip.
See this Your engineer probably never checked how freely the gear moves by hand; it’s a tricky process which involves either dismantling the locks, or using the hydraulics to just-unlock the gear and then you can move it by hand.
I think people on this forum think to negative about engineers. The gear is very easy to move by hand, as you can push it out of it´s lock with one hand (do not try this with the aircraft on the ground, the gear will colapse). Even with relative low friction your gear will not swing fast enough to get into locked position with emergency gear. I can not believe there are engineers who would skip this emergency gear test for example.
The gear is very easy to move by hand, as you can push it out of it´s lock with one hand
One would normally avoid pushing sideways on anything, when on jacks.
I am also not at all sure one can push the TB20 gear out of lock with just one hand. It would make it very easy to get a gear collapse when landing. From that standpoint, the gear is locked solid. The hydraulics are needed to move the locks, but the hydraulic linkage operates the lock mechanism first, and only afterwards it moves the main gear mechanism, so it has an “advantage”. If you have a plane on which you can unlock the gear just by pushing on it, surely that yould be completely useless for landing with?
OK, you could dismantle the hydraulics and then operate the lock by hand, but that is more than most people do at the Annual.
Yep, copy all that ‘gear lock’ talk. I always thought the system used was the age old engineering trick called ‘over centre’.
This was used on the old glass pop bottles where you push the wire stopper mechanism beyond a certain point and it would ‘lock’.
The knuckle of the mechanism is moved back beyond the centre line and the system would un-lock.
You see the same ‘over centre action’ on the locking system on the canvas sides of trucks as the driver clamps them all down.
Going back to the original thread “premature camshaft failures” I can report that I am waiting for the return of our group owned DR400/180 that is having a replacement overhauled engine(0-360) The old unit (original) made it to 2150 hours. In that time (21 years) it had had 3 of the 4 cylinders replaced and fortunately never had a problem with metal in the oil etc. In fact the main reason for bringing forward the engine replacement was because of a persistant oil leak which according to our engineer was caused by “fretting” ( the two halves of the crankcase rubbing against each other as a result of incorrect torque settings when one or other of the 3 cylinders were replaced). We shall keep a wary eye on the new engine!
From that standpoint, the gear is locked solid.
As Warley wrote correctly, it is in over centering action. Forces on the landing gear will act up the locking mechanisme, trying to overcenter the part further, which is mechanically limited, so it will lock solid. To unlock their is little force required, This (opposing) force is applied such that it goes out of overcentered position.
If you have a plane on which you can unlock the gear just by pushing on it, surely that yould be completely useless for landing with?
You don’t unlock it by pushing the gear, you do that by pushing the downlock. Even on some of large airliners I worked these can be unlocked by hand. There are also several accidents with these, where someone unlucks the gears, and the gear collapses.
Example of poor overcentering on a Commache seen on youtube:
