I was looking at my time-life component sheet last night and was doing a bit of research on something called the ‘no back spring’ which has to be replaced every 1000 hours. It’s part of the gear actuator that performs some sort of safety function and both the electric and emergency mechanisms depend on it.
The spring which is no bigger than a stack of a few 2 euro coins goes for $800+.
It seems Mooney has had various actuators over the years including Eaton, Dukes, and Plessey. Although the parts catalog suggests my S/N should have a Dukes, the sheet says mine is a Plessey and they apparently don’t support their actuators or make the springs meaning that in theory I’d require a new actuator at 1000 hours which even for an overhauled one will be in excess of €10000 and closer to €20000 new. I’ll dig through the logs whenever I get them back to make sure.
There has been much debate on MooneySpace even by people who can just replace the spring as to whether to bother because of the risk of infant mortality (there have been some cases). There is also talk of Mooney extending the recommendation to 2000 hours but it hasn’t happened yet.
Given that those in FAA land seem to have a choice over whether to do it or not, is that the same for EASA regs? It’s in the mx manual as a ‘recommendation’. It’s currently in my mx program but I’m wondering if whenever I move to SDMP when EASA brings it in, if I can just leave it out and run the spring ‘on condition’. I assume it would almost be cheaper to go N-reg than replace the actuator unnecessarily. Thankfully I’m 600 hours away from it yet, but I’d like to know if I need to increase my hourly reserve by €20!
zuutroy wrote:
It’s currently in my mx program but I’m wondering if whenever I move to SDMP when EASA brings it in, if I can just leave it out and run the spring ‘on condition’.
You mean when ELA finally comes for planes above 1200 kg? Yes you should be able to do that.
However, the question is whether you can’t source a Plessey one from someone like Don Maxwell or LASAR, who might have stock on them or ask if Alan Fox has one which has less than 1000 hours on it. If you really have one which is no longer manufactured, it might be an idea to get one while people still may have them in stock. I wonder if Mooney have some? If so, rather have an 800$ spare then having to replace the actuator.
I’d also keep asking Mooney and encourage others to do so as well… if it gets too much time consuming for them, they might press for this. Also you’d have to check if the spring is specific to the actuator, which some people seem to think it is not. Again Don or the folks at LASAR might be able to shed a light a tad more efficiently than Mooney themselfs.
What happens if that spring fails?
There are stories of people stumping up for a new actuator, so I’d imagine there is no supply of springs as one would think those people would have exhausted every avenue before doing so.
If it fails on the way up the gear won’t come down again. If it fails on the way down, the gear won’t come up again. Apparently the whole thing was triggered by a dodgy batch of springs in the 90s and there are people with airframes approaching 10k hours that visually inspect them each year and find no problems.
As far as I understand it, it is difficult to spot if a spring is likely to break in the next few hundred hours / year, so if you go onto an inspection schedule you are taking a risk. So the question is what happens if it does, and at the worst possible moment?
If the result is that the gear stops in a random position (including fully up or down), and the manual extension still works in that case, then it is not a high risk, and I personally would be inclined to take it to save 10-20k, but not to save 1k.
If the gear can get stuck and blocked up or half extended, or could end up not “locked” – I would cough up.
Might be worth to open the floor and have a look what you really have. If it is a Dueks then it is the same unit as fitted to the Comanche and maybe the Comanche Gear guru; Matt Kurk will be able to help you. His shop website is www.comanchegear.com
Good luck
Given that those in FAA land seem to have a choice over whether to do it or not, is that the same for EASA regs? It’s in the mx manual as a ‘recommendation’.
Seems like this question depends on the EASA member. For example, Swiss FOCA generally treats manufacturer recommendations as mandatory work, whereas this is not necessarily the case in France or Germany.
(To be more specific, according to FOCA TM 02.020-35, “Instructions for Continuos Airworthiness” are mandatory. Manufacturer recommendations typically fall into that scope.)
Zorg wrote:
wiss FOCA generally treats manufacturer recommendations as mandatory work
On what legal basis, or just sheer inertia?
Zorg wrote:
whereas this is not necessarily the case in France or Germany.
So I guess as I’m F-reg that whenever we get to self-declared mx for ELA2 I can take it out. I’ll just bring the spring to the scanning electron microscope in work each year instead :)
Cobalt wrote:
On what legal basis, or just sheer inertia?
For the curious, here are links to the relevant documents (in German, sorry):
“TM” means “Technische Mitteilung” (i.e., “technical notice”).
