Timothy wrote:
The break must just have happened, the way things do sometimes just fail.
…and it may be that this (rather critical) weakness was designed out of later PA31s; I don’t know, but presumably they didn’t know that it was fragile when they designed it.
It had recently had some very thorough maintenance, with multiple engineers duplicating inspections, so I really don’t think that maintenance or inspection can be blamed.
And, to be fair, Piper did design in the standpipe arrangement to ensure that the emergency system worked.
But, having said all that, I do wonder if the engineers ever really studied that pipe or joint and thought “single point of failure”?
I have been an owner since 2002 and actually I could take my plane to a different company each year and each damn time I would be amazed staggered to find what has not been done that is bloody obvious on a 100 millisecond look and by implication what other stuff has not been looked at (in the literal sense) never mind seen a “maintenance procedure”.
I have done informal prebuys on TB20s where I walk up to the gear and waggle the gear doors and if (as usual) they are seized solid, it’s obvious in the first minute what the rest of the plane will be like, and then the only debate is whether the seller is willing to discount the price by the amount of replacing half the control linkages and everything else that moves.
So, to me, anything is believable.
The fixed wing business hangs together largely because it is really hard to make a plane fall out of the sky due to dodgy maintenance. You need a wing to come off, or similar. I recall only some 10% is due to maintenance. Perhaps more gets unreported because the pilot was able to deal with it.
But to be fair to companies, they are not required to do a 100% eyeball of everything that is visually inspectable. They need to comply with the MM, or LAMP or whatever. And e.g. the Socata MM is soooo detailed that nobody does much of it, so you get the other extreme. A basic Annual done IAW the TB20 MM would be €10k, plus any remedial action. I have just been helping with one such Annual – see postings here and it was the first time some subtle bits of the gear got lubed since manufacture.
The standard £2500 Annual gets most of the tasks skipped.
I reckon your Piper PA31 hydraulic pipe break may well have been spotted, but I can also see that nobody in the trade would have spotted it unless they just happened to be staring at the joint. Prob99 there would have been fluid leakage… then one asks whether the fluid level had been checked at the 50hr or (as maybe 1% of owners do) or only at the Annual 
Peter,
We have discussed many times before, and you always get upset when I say it, but I don’t really know why, that our experience of both maintenance companies and avionics companies is poles apart.
We have discussed many times before, and you always get upset when I say it, but I don’t really know why, that our experience of both maintenance companies and avionics companies is poles apart.
Not sure that’s true… what about the inverted ILS which got you chucked off the airport when you filed an MOR on the avionics shop, Timothy? I will limit what I transfer from other forums, since my memory is not as good as it used to be and I don’t have time to search for stuff for no reason. And what about that flight across London with a cylinder hanging off, most likely due to over-torqued and stripped cylinder bolts? You posted the photos of it, too.
I don’t get upset – I don’t need to My biggest “problem” is that I know where a lot of skeletons are buried. Of course much of it I got in confidence so can’t post it, and people know that, too 
Ultimately, 99% of owners never look under the covers. And 99% of those who do and find something, keep quiet because they want to maintain relationships. They even tell me exactly that. I don’t have a lot of relationships to maintain, with my plane not serviced by a company and with everything many years out of warranty.
Back on the topic, retractable landing gear is a particular problem, not because of any inherent difficulty or complexity, but because it is labour intensive to lube it properly. Lubing can be done effectively only with grease, so the traditional time-saving method (spray lube) can’t be used. But you can’t get grease in there (except where there are grease nipples, which is rare on SEPs and MEPs) without a complete dismantle of the mechanism, which takes several days and is prone to problems with e.g. springs flying off, the need for special tools, etc. I have seen this done on King Airs and TBMs (I was hangared there) but those owners just paid any size bill, and sure enough they got them! Every service was 5 figures plus.
In 46 years of flying and quite a few thousand hours on a fairly large variety of types, the number of faults I have had as a result of poor engineering or inspection has been tiny.
My memory may be no better than yours, but I seem to remember you being quite didactic on the subject of that detached cylinder being as a result of the considerable age of the engine; now you say a wrongly torqued stud. Well it could have been either or something else, the jury is out.
The reversed CDI was indeed appalling, probably the worst bit of engineering I have seen, but that was done by one of the better respected and more expensive engineering shops – Alan Mann.
I have had since then three very big avionics refits, two of them effectively bare metal with every wire stripped, and one very large but not quite starting from scratch. All three were as close to faultless as anyone could expect.
The most recent, which was new metalwork, dual Aspens, GTN750, GTN650, ADF, DME, 3rd 8.33, GTX330ES, GTX330, TAS605A, WX500, GMA340, Bose Lightning and EDM790 all connected to a 1960s autopilot, and everything else moved around, has not been back to the shop for a single glitch. (Bournemouth Avionics at Lee on Solent, highly recommended, no business connection.)
I have had my share of failures, arguably more than my share, but they have mostly been component failures. The only one that kept dogging me in the Aztec was fuel icing, and that was engineered and inspected to death – no-one could accuse the engineers of being slack or careless, they tried everything they could, but everything checked out perfectly according to book.
I think that the main reason that light aircraft keep failing is not poor field engineering, but the need to build them as flimsily as possibly to maximise payload and performance. That means that everything, including all the ancillaries, is just a little too thin and light, and the whole caboodle is just good enough.
I think that the main reason that light aircraft keep failing is not poor field engineering, but the need to build them as flimsily as possibly to maximise payload and performance. That means that everything, including all the ancillaries, is just a little too thin and light, and the whole caboodle is just good enough.
I am sure that’s true. I was hangared at a turboprop place for 10 years and the build quality is totally different (except for the PA46T which is “standard SEP”).
I have to maintain that probably the reason I become aware of bad work is because I participate in all servicing, to an extent greater than any owner I have ever known around here. I could post specific examples of stuff I spotted on other planes which the owners never spotted but it would not be very kind to them, and a bit pointless.
Peter wrote:
different (except for the PA46T which is “standard SEP”).
I would disagree with that. The Meridian is very well engineered. Mine was faultless. The jet prop is cleverly engineered but is a converted Mirage so they do have to work with a number of the piston systems eg environmental.
…but is it not true to say that all three (Meridian, Mirage and Jetprop) pay for their relative over engineering in rather lacklustre payload?
Timothy wrote:
…but is it not true to say that all three (Meridian, Mirage and Jetprop) pay for their relative over engineering in rather lacklustre payload?
Yep, I would say that is fair. The Mirage however has excellent range s payload if you are prepared to fly it LOP.
