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Twin loss of control - UK

Piper Aztec flaps are hydraulic. However, most Aztecs only have one engine driven hydraulic pump, so you have to know which engine, ‘cause if that one quits, you’ll have to pump them up (along with the gear) while you configure the plane for single engine climb out – it gets busy for a minute in the cockpit.

Just to be clear, while this is quite true (and the weakest link in the Aztec’s safety chain, which is generally very strong), it has nothing to do with Asymmetry. In the Aztec, the two flaps are connected by a very tough torque tube, which had to be replaced by AD recently, so they are all young.

Because of the single pump (which is on the left engine, making the left doubly critical) I always rotate at blue line and whip the gear up as soon as the wheels are off the ground. That means that if the left engine fails, even the residual turning, before it feathers, is likely to get the gear up, or most of the way up. Also, no flap on take-off for the same reason.

In the go around from very low (I am not talking about a Missed Approach go-around, where you have 200’ in hand, but a visual go around from 10’) my technique is to apply only enough power to fly level along the runway, get the gear and flap up, then apply climb power. All of this to manage the risk of losing the left engine in a high power, low speed, flaps and gear dirty scenario.

These are the kinds of calculations you have to make when working with risk on light twins.

But if Bloomer won’t fly with me, I am sure I can find other people

EGKB Biggin Hill

“Properly trained” is one thing … STAYING trained the other, and the more important one. I WAS properly trained for multienngine aircraft amd at the end of the course (Seneva V) i was very good at it. But 5 years later I was UNSAFE. And that’s how it goes many times, with PPL. IFR, Aerobatics. multiengine …

This is perhaps more an argument for not flying that plane rather than manual flaps…

and walk home from the middle of the desert?

thanks but no thanks

LSZK, Switzerland

Because of the single pump (which is on the left engine, making the left doubly critical)

Can one install a second hydraulic pump, onto the other engine?

Funnily enough I bought the Lyco P/N 71675 hydraulic pump adapter, shown in the pic here, but I can’t use it because it fits an IO540-C4, but not my IO540-C4D5D. So I was going to stick it back on US Ebay…

I did wonder why some people are driving a second hydraulic pump, via this adaptor… clearly it must be for the landing gear, or flaps.

Administrator
Shoreham EGKA, United Kingdom

Can one install a second hydraulic pump, onto the other engine?

Well, I have had different stories, the most recent of which is “no”.

EGKB Biggin Hill

Ted Smith must have had an aversion towards hydraulic pumps, because this is the second twin of his design in my ownership certified without that redundancy. Thankfully, the Aerostar has an STC to put an electrically driven auxiliary hydraulic pump in and I’m rather happy it came with that. It’s a bloody stupid design – they have redundancy in most things that are not nearly as important as the hydraulics and I can’t help but wonder – why? Cue an engine failure on takeoff in any of these on the bloody gear comes out! Nevermind trying to eke out a climb. I’d much rather have an extra hydraulic pump than an extra alternator.

And tying into another post you did Peter on another subject: I hope with the revisions of FAR 23 that solutions that actually improve safety very considerably will find a way to get approved in the future. I looked into putting a second hydraulic pump on the right engine on the old Commander, but there was no way of doing so legally. Even though there was an empty space on the engine at the accessory case. Nope, couldn’t be done. Looked into taking an STC electric aux hydraulic and tying that in, but that would have to be STC’d at great cost, so no.

They’d rather we kill ourselves than have non compliance. You have been assimilated.

Last Edited by AdamFrisch at 20 Nov 00:47

I looked into putting a second hydraulic pump on the right engine on the old Commander, but there was no way of doing so legally

Sure – it is a Major Alteration, for which there is a route. For example, look through my certification notes here. Being US based, no problem for you. You don’t need an STC…. (What I don’t doubt is that your A&P says you do but that’s because he can’t read the regs – a common problem).

Well, I have had different stories, the most recent of which is “no”.

From who?

Last Edited by Peter at 20 Nov 07:41
Administrator
Shoreham EGKA, United Kingdom
47 Posts
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