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G-BJNZ Aztec removed from register

Ibra wrote:

I gather flying ILS 3deg (IMC) is possible on one engine? Yes flying circuit in Southend would have resulted in same outcome as circuit in Elstree…talking to ATC does not change much other than getting instant SAR on crash

If you know that you can’t maintain altitutde when high enough and arrange the approach accordingly, this is manageable. If you find out the first time when you level off at 2,000 ft 5 miles from the airfield, it’s too late…

Biggin Hill

Cobalt wrote:

If you know that you can’t maintain altitutde when high enough and arrange the approach accordingly, this is manageable. If you find out the first time when you level off at 2,000 ft 5 miles from the airfield, it’s too late

Yes there was no guarantee that VFR/IFR in Southend would have worked neither (not without leveling up and keeping it tight)
I still think the continuous descent to hit 3deg ILS is doable with 81% power on one engine in light winds?
Same interesting topic comes up with icing during an ILS

ATC are likely to drag it up on 6nm vectored ILS with aircraft not able to keep altitude with one engine but at the end of the day it’s up the pilot to figure out his shortcut, descent profile, aircraft config, extra speeds and get it right on first time…there was no go-around: it’s outgoing only today !

Paris/Essex, France/UK, United Kingdom

Yes, when you know you’re way down on power (losing an engine in a light twin constitutes ‘way down on power’ even if the engine still operating is perfect) then you don’t throw height away before you have to.

I’ve only once flown an aircraft which I suspected was down on power and/or about to lose the engine. It seemed obvious to me to keep as much height as possible until the last moment and then stuff it down a steep approach with crossed controls. I don’t recall planning that as a strategy or doing any TDODAR – it just seemed blindingly obvious.

EGLM & EGTN

Anyways, 43 years old engines, even if not flown that much, are an example why we should set up an ‘aging aircraft initiative’ as the FAA did?

My single Lycoming is currently at 52 years since assembly Power output looks to be OK per climb rate and fuel flow. Oil consumption is currently about 1 quart every nine hours – I know there’s some light corrosion in three of the four cylinders, which will probably over time take its toll on the piston rings, but it’s working fine for now and is still not much more than a mid-time engine by operational hours. There’s never been any material in the oil filter – which is where spalled cam and lifter material is generally found. We take a look at it every year and there’s yet to be any reason other than concern about the unknown to take it apart. No FAA policy applies to any of the above.

It would be a little harder to verify engine power on a twin. Static RPM is one way to do it, other than fuel flow and climb rate.

Last Edited by Silvaire at 19 Jan 15:18

I don’t really read that much into the AAIB reports these days.

The engine wasn’t developing 81% power as 3 of the plugs had to be cleaned of lead deposits before the engine would run smoothly.

How many hours had the aircraft done following the annual? And how much of an ‘annual’ had the aircraft had? I have certainly known aircraft to come off an annual where the plugs hadn’t even been removed yet alone inspected.

Of course this was all done at an approved organisation so it was all done correctly. Part ML has never been popular with the powers that be. I’m surprised they didn’t recommend 62 day checks and a star annual.

Now if they had run on UL91 then those spark plugs wouldn’t have been leaded up and the engine would have developed 81% power. Now I’m not saying an Aztec would stay a float on 81% power but it would of given you more options.

I will be flying an Aztec E privately this year belonging to some customers. They needed a six-seat twin to fly from Ireland to the UK/France mainly during the summer, with an experienced CPL flying it. They needed something which had to be very comfortable on grass strips. The Crusader would have been an option but the useful load is too low, the same as the Seneca. The 310R and 58 Baron would have been a lot more money. My business partner already maintains an identical E model to the one we sourced, so there is no discovery time on the maintenance. Yes, it will burn 100-110L of Avgas per hour, but if you are making money when you arrive that’s not an issue. A good mechanic will know by removing the rocker covers if the cam is worn, and I think we can rise to cleaning some spark plugs

Buying, Selling, Flying
EISG, Ireland

@WilliamF the E is the best, and when well maintained, very docile and reliable.

I once took one from Weston to Bucharest, quite a slog but perfectly doable, with a comfort stop at Augsburg.

Oxford (EGTK), United Kingdom

Bathman wrote:

How many hours had the aircraft done following the annual? And how much of an ‘annual’ had the aircraft had? I have certainly known aircraft to come off an annual where the plugs hadn’t even been removed yet alone inspected.

Of course this was all done at an approved organisation so it was all done correctly. Part ML has never been popular with the powers that be. I’m surprised they didn’t recommend 62 day checks and a star annual.

The report certainly screamed pencil-whipped annual at me. It should lead to a very uncomfortable meeting between the maintenance organisation and the CAA, but I doubt it will.

I came to aviation maintenance a little late but had plenty of experience maintaining cars and dealing with garages. Thus I came with the mentality that just because they filled in the paperwork saying they’d done it and invoiced you for doing it, it didn’t mean they had actually done it. In fact, the working assumption was that they hadn’t done it, unless you either trusted them on a personal level or saw physical evidence that they had.

Surely you can measure camshaft wear without splitting the crankcase by measuring the lift at the rockers. It may not be in the scope of work, but if the engine is old and camshaft wear is a known thing, I’d be doing it. There’s little excuse for that engine having got through an annual developing 81% power at best.

EGLM & EGTN

That’s an impressive report

An engine had to have a comprehensively shagged camshaft to develop 81% of rated power due to the camshaft wear.

There is a famous accident report out there where the engine was extracted from the wreckage and the camshaft had about 5mm missing from the lobes (!!) and it was still developing something like 80% power.

I could probably find it; it may be linked on EuroGA somewhere. It was one of the “famous” ones – a bit like that fatal crash of some PA28 or some such which was being run on some homemade mystery fuel which defied all attempts at analysis but which was found on dyno test to be as good as 100LL

But also if so much metal was gone from the camshaft, it would show up heavily in oil analysis (yes I know few owners in this community will be doing that… “why bother when you have a spare engine” is the usual phrase used) and probably in the oil filter, because once the case hardening goes (it is around 0.050" thick, only) the rest goes pretty fast, and not in tiny pieces either.

OTOH the damaged lobes were just two inlet valves so probably not much of an effect

Administrator
Shoreham EGKA, United Kingdom

There is a famous accident report out there where the engine was extracted from the wreckage and the camshaft had about 5mm missing from the lobes (!!) and it was still developing something like 80% power.

In this case too the wear on one inlet cam lobe is approximately that amount, about half the intended cam lift and the quoted power reduction is about the same. A single camshaft lobe was worn here, but it lifts the inlet valves on two opposing cylinders, of six.

As I mentioned above, power reduction due to camshaft lobe wear is more closely related to a reduction of area under the lift versus angle (or time) curve than to the percentage lift reduction. The initial wear removes little area under that curve due to the cams limited duration at highest lift. As it wears more, the effect of each increment becomes greater, but extreme wear like e.g. 25% reduction of lift does not mean 25% reduction in power.

This makes the engine relatively fault tolerant, and it is simple to check for the substantial reduction of valve lift that would cause a meaningful reduction in power.

Yes, when the cam starts coming apart, the pieces coming off the cam are large and end up in the oil filter. Oil analysis would probably give an indication also, but the clearest and most obvious way to know is to inspect the filter element.

Last Edited by Silvaire at 20 Jan 16:04
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