Another video showing close-up door operation
What matters is that the door is (a) tight and (b) correctly located when the gear is UP i.e. you need to test this on jacks. The adjusting link on the door is tweaked so the door is held at just the right (perfectly flush) position when the gear is UP.
The play on the door is a bit worrying but it’s a bad design, with some female parts made of mild steel which have steel pins in them, but the holes are open-grooved all along
so any grease you put in there escapes on the first flight. So the linkage wears quite quickly. The female parts (pic above) are about $300 each (2014 price so probably 2x now) and there are four of them. The female parts should be made of phosphor-bronze, or at the very least the holes should be normal closed holes so that grease can be properly retained. If you ever get somebody to make some for you (under the FAA owner produced parts regime) the solution is obvious. There is also another obvious mod to the gear door itself, where a steel pin goes through a 1.5mm thick aluminium flange and obviously wears it out; there should be proper bushes in there, but then the pin ends up too short so a new one has to be made.
And this is the emergency gear release
All cleaned and freshly greased
I paid multiple firms over the years extra money to properly grease the entire landing gear but, as per standard GA maintenance practice, it was never done since the plane was new in 2002 – till today. It’s quite interesting… inside the spring shown is a telescopic spring guide
and if that gets clogged up or corroded, the lock may not work, so the down-lock will be relying on hydraulic pressure entirely, leading to a gear collapse when you go around a corner…
The depiction in the MM is rubbish but it is item 110
Mine was fine but definitely needed greasing.
I am doing all this because the engine is away for 3 weeks, so we have extra time.
Just normal operation for hydraulic gear.
That certainly proves the point. Shows what a good idea it is to video and archive gear retraction tests. I guess the only reason my system produces a different response is that it has downsprings on the MLGs (bungees actually), which build up resistance such that the other MLG starts to move. If the TB20 doesn’t have MLG downsprings, and with short legs reducing the lever arm, perhaps the resistance build-up is just not enough to overcome the inertia in getting the other leg moving.
Here is one from 6 months ago
I should add that during the Annual just done we did test the emergency gear release – as we always do when we have the jacks to hand – and the gear fell down perfectly.
Notice that 6 months ago one gear came up first almost entirely, but on the last one the other gear came up first almost entirely. So I think there isn’t anything sticky. I can’t see the “something sticky” magically moving itself from one side to the other.
Also on this Annual every joint on the gear – that doesn’t already have a grease nipple – was dismantled and packed with grease.
Is think that there is some misunderstanding here, the TB20 & most other light aircraft use a hydraulic system and it is the leg that has the least resistance to movement that moves first with the others following in resistance to movement order as the hydraulic pressure is applied.
This true, it is normal for hydraulic controlled gear. When at an airfield take a close look at a Socata TB20, most Cessna single engine, Piper Saratoga, Piper Chieftain, they will all show a difference in gear movement between the gears. On the Cessna 182RG / 210 / 337 it looks quite strange, as during gear extension, the gear drops, looks strange, and after a second or so it will move further to it’s looks. On some Cessna’s there is a single actuator for both MLG, on most their are two actuators, as with the other listed aircraft.
If I remember correctly the Mooney and the Beech Barron / Bonanza have electrically drive mechanical systems and so the legs are locked together in terms of order of movement.
This is true as well, so these gears always travel synchronised due to nature of their drive system, If those would behalve such as the TB-20 there must be something very wrong with the gear drive system.
The TB20 system is very simple, I have a similar system on my aircraft. As stated I would agree the leg with the least resistance would start moving up first. If the load remained the same throughout the retraction sequence the legs might even retract one at a time – but the load increases considerably as the leg raises. As the leg nears full retraction the load is several times greater than at the start of the sequence. However even this big increase in load is not enough to start the left MLG moving until the right MLG is fully retracted. Furthermore when the gear extends the left MLG is again much slower to move than the right MLG. If this was my aircraft I would suspect that the left MLG was stiff mechanically or there was an internal leak in the jack. If there was a leak in the jack this would show up in flight with more frequent “blips” from the motor to maintain pressure, so this is unlikely. It is also not a problem with a sticking release latch either as all the legs clearly unlatch at the same time.
I doubt this is urgent but it is definitely an odd retraction sequence for this type of system.
If I remember correctly the Mooney and the Beech Barron / Bonanza have electrically drive mechanical systems and so the legs are locked together in terms of order of movement.
Correct (for the Mooney at least)
