Aztec engine-out procedures

[Jdm]

My question is for anyone who has experimented with shutting down a left engine on a Aztec F model equipped with only one engine driven hydraulic pump. I’d specifically like to know if the rotational speed of the dead (unfeathered) left engine is enough to provide sufficient EDP pressure to raise the landing gear? I know this would depend on airspeed so lets say a prop rotational speed equivalent to approximately blue line.


Appreciate it..

 

[mondtster]

Pressure isn’t important. The movement of hydraulic fluid is...

Keep in mind that the hydraulic pump is a fixed displacement pump; in other words it will move a certain amount of fluid per revolution. If the engine is turning slower (and assuming there is nothing broken in the accessory drive) it is going to take longer for the fluid to be pumped to move the gear. It will move, but not as quickly as it would if the engine is turning faster.

 

[Jdm]

Ok, good point.

Substituting “movement of fluid” for “pressure”.

Now, I’d specifically like to know if the rotational speed of the dead (unfeathered) left engine is enough to provide sufficient movement of fluid by the EDP to raise the landing gear? I know this would depend on airspeed so lets say a prop rotational speed equivalent to approximately blue line.
Assuming the engine is not seized obviously.

 

[Kristin]

A windmilling prop on a Aztec is more drag than having the gear hanging out. So the correct procedure is to feather the engine and then work your right arm on the hand pump.

 

[Jdm]

A windmilling prop on a Aztec is more drag than having the gear hanging out. So the correct procedure is to feather the engine and then work your right arm on the hand pump.

Yep. I understand the drag consequences and the procedure. I would like to know the answer to my question if anyone happens to know. I would also like to know approximately how long it might take to fully raise the gear in the condition stated above.

Thanks.

 

[GRG55]

I'd be surprised if anyone knows the definitive answer to that question without actually trying it.
And that seems a low probability event for the reasons in #4. It would be a highly unusual procedure indeed. But you never know...somebody here might have tried it.

 

[Jdm]

I understand. Was just trying to get an idea. Apparently it takes about 50 pumps of the handle for a full swing in either direction. Assuming an engine is lost right after takeoff it seems reasonable that at least some of the gear travel would be accomplished by the turning EDP while identifying, verifying, and feathering takes place.

 

[Tantalum]

If you think about it, you are basically using a giant windmill to move around and compress the air in six cylinders and then turn a hydraulic pump just so you can get some gear movement out of it.. that's an awful lot of drag and likely not a reasonable tradeoff

Much safer to just feather the thing and put your hand to work

Also why you want to get that gear up as soon as practical

 

[mondtster]

Why the obsession with asking the question in context to putting the gear up? I really doubt anyone would be doing that procedure. Putting the gear down on the other hand is something that many people have likely done. I can tell you that a windmilling prop will allow the engine to turn fast enough to move enough fluid to put the gear down, although I’ve never bothered to time it.

 

[Jdm]

If you think about it, you are basically using a giant windmill to move around and compress the air in six cylinders and then turn a hydraulic pump just so you can get some gear movement out of it.. that's an awful lot of drag and likely not a reasonable tradeoff

I appreciate it. I‘m very clear on this and have been for at least 20 years.

Much safer to just feather the thing and put your hand to work

I totally get this also. It’s not exactly in compliance with what the POH says, but it’s in accordance with every advanced publication I’ve ever read.

Why the obsession with asking the question in context to putting the gear up? I really doubt anyone would be doing that procedure. Putting the gear down on the other hand is something that many people have likely done. I can tell you that a windmilling prop will allow the engine to turn fast enough to move enough fluid to put the gear down, although I’ve never bothered to time it.

Also why you want to get that gear up as soon as practical

Gear up is just as important as down. Not trying to downplay down haha, but when taking off at weights close to max it’s very important to obtain optimal climb performance in certain areas. 50 pumps is a lot! I’d like to get an idea of how much is remaining to pump.

 

[Jdm]

Here’s a pic of the POH. They place pumping the gear up ahead of feathering in the emergency procedure, not that I agree, but it’s interesting enough.

 

[Tantalum]

Here’s a pic of the POH. They place pumping the gear up ahead of feathering in the emergency procedure, not that I agree, but it’s interesting enough.

Interesting indeed. You know, I'm not saying you should, but you could try this, just go to 8,500 AGL min and put the plane in a takeoff configuration, stay at a safe airspeed and give it a shot on your next engine out practice

 

[Jdm]

You know, I'm not saying you should, but you could try this,

I’m definitely planning to work on drag demos. 8500AGL seems rather high though. Book says to expect more pumps at higher altitudes. Problem is the company’s flight execs don’t appreciate too much extra training in their airplane unless it’s absolutely necessary. I respect that and will try to fit it in on the next round.

 

[RussR]

I teach a lot of multi. In light twins like this, my mantra is "if the gear is still down when an engine fails, we're pulling both throttles to idle and landing on whatever is straight ahead". And that's even in planes where the gear works just fine with the engine out. There's too much to do, in too short a time, and too much risk of turning a survivable event into a fatal accident, to bother with trying to get the gear up in this situation.

An engine fails with the gear down and you don't have any runway remaining? The insurance company just bought the airplane. Make sure you don't buy the farm.

 

[mondtster]

I teach a lot of multi. In light twins like this, my mantra is "if the gear is still down when an engine fails, we're pulling both throttles to idle and landing on whatever is straight ahead". And that's even in planes where the gear works just fine with the engine out. There's too much to do, in too short a time, and too much risk of turning a survivable event into a fatal accident, to bother with trying to get the gear up in this situation.

That’s essentially what I’ve always taught as well, and my mentality when it comes to flying piston twins.

 

[Tantalum]

I’m definitely planning to work on drag demos. 8500AGL seems rather high though. Book says to expect more pumps at higher altitudes. Problem is the company’s flight execs don’t appreciate too much extra training in their airplane unless it’s absolutely necessary. I respect that and will try to fit it in on the next round.

We did our engine out work at a pretty high altitudes but there's also terrain around where we live.. 8,5 msl over the Salton Sea is actually a little higher since the salton sea is below sea level

We have an Aztec in the club but no multi training in it. Understandable..

 

[Jdm]

I like the way you think RussR. Problem is there’s not always a survivable area to touchdown, and then there’s IMC and night ops to deal with also. I think it’s best to at least chair fly the critical situations.

 

[GRG55]

I teach a lot of multi. In light twins like this, my mantra is "if the gear is still down when an engine fails, we're pulling both throttles to idle and landing on whatever is straight ahead". And that's even in planes where the gear works just fine with the engine out. There's too much to do, in too short a time, and too much risk of turning a survivable event into a fatal accident, to bother with trying to get the gear up in this situation.

An engine fails with the gear down and you don't have any runway remaining? The insurance company just bought the airplane. Make sure you don't buy the farm.

"...turning a survivable event into a fatal accident..."

I continue to be surprised at how many emergency responses seem to focus on saving the airplane instead of saving the occupants. This applies to single engine failures also (the classic "try to extend the glide" being one example).

 

[GRG55]

I’m definitely planning to work on drag demos. 8500AGL seems rather high though. Book says to expect more pumps at higher altitudes. Problem is the company’s flight execs don’t appreciate too much extra training in their airplane unless it’s absolutely necessary. I respect that and will try to fit it in on the next round.

Understandable given the expense. But the expense of an accident from an incorrect response may be higher (but it's clear from your posts you know that).

Early in my career I spent quite a few years in the production and processing of sour gas. H2S is deadly. In the late 1970s/early 1980s the fatality rates in the industry were unacceptable. In particular there were several sequential double fatalities where the apparently trained and properly equipped safety man died. I participated in the root cause analysis work, assessment and subsequent situation specific training enhancements that were made through an industry collaboration. The results were dramatic. Part of that process was recognizing the "instinctive" but negative outcome responses and "training those out". That experience stuck, and factors into my approach to my personal flying.

The closest analogue I can think of in GA is the work that Cirrus has done with its training program over the last decade, with similarly large tangible improvement in the fatal accident rate.

I fly purely for fun and pleasure. But I have doubled the frequency (every 6 months) which I am in the Club simulator reviewing my emergency procedure responses for my Aztec. Unfortunately, I can't simulate your critical engine scenario to help you get the answer you are looking for. When I went looking for an Aztec dual hydraulic pumps was high on my list of requirements as part of the risk management criteria I drew up.

 

[Computerjim]

My mantra just before take-off -
If on the ground, shut it down
If the gear is down set it down
If the gear if right it just might (fly)

It is all about airspeed and controllability.

 

[Dave Theisen]

I suspect it will take longer for the gear to come up than it will to hit the ground.

 

[Kristin]

In another life, I was the 135 instructor and check pilot for a few planes, one an E model Aztec. At the typical weights that we flew, which was usually 400# or so below gross weight, once the engine was feathered she would hold altitude or even climb very slightly on one engine, with the gear down. In reality, that would only be a factor in a takeoff right after rotation and there were only a very, very few circumstances where one would continue to fly the plane, rather than putting it back down.

More practically, the gear is somewhere in transition as you pass 100' or so when the engine fails. If the engine feathered quickly enough, there is a possibility of keeping it in the air on one engine. The Aztec is a pretty forgiving airplane. More so than most.

 

[Kenny Phillips]

Pressure isn’t important. The movement of hydraulic fluid is...

Keep in mind that the hydraulic pump is a fixed displacement pump; in other words it will move a certain amount of fluid per revolution. If the engine is turning slower (and assuming there is nothing broken in the accessory drive) it is going to take longer for the fluid to be pumped to move the gear. It will move, but not as quickly as it would if the engine is turning faster.

Pressure can be very important; as soon as a load in introduced, the prop may slow even more, or stop! Perhaps not likely, but possible. Oldsters will remember how their car's idle speed would drop when the headlights were turned on.

 

[mondtster]

Pressure can be very important; as soon as a load in introduced, the prop may slow even more, or stop! Perhaps not likely, but possible. Oldsters will remember how their car's idle speed would drop when the headlights were turned on.

It would probably be beneficial if there was a discussion on how the Aztec gear system works here...

Pressure is important but only at one or the other end of the gear/hydraulic cylinder travel. As I wrote earlier, I’ve extended the gear many times with the engine windmilling. There is sufficient hydraulic oil movement to move the gear and build the necessary hydraulic pressure at the end of the travel.

And yes, I am also well versed the idle droop you describe.

 

[Jdm]

another life, I was the 135 instructor and check pilot for a few planes, one an E model Aztec

Thanks for the performance insight.
Did y’all happen teach the book response (post # 11) for engine failure right after liftoff, or the feather first technique that most of us were taught in primary training? There seems to be a large discrepancy in regards to the order of how most of us would handle this situation in comparison to the book answer. Trying to determine if the book is correct in implying that gear is more of a drag penalty than a windmilling prop??

 

[Clip4]

Thanks for the performance insight.
Did y’all happen teach the book response (post # 11) for engine failure right after liftoff, or the feather first technique that most of us were taught in primary training? There seems to be a large discrepancy in regards to the order of how most of us would handle this situation in comparison to the book answer. Trying to determine if the book is correct in implying that gear is more of a drag penalty than a windmilling prop??

The POH provides the procedures and I teach the procedures specified in the POH along with a heaping helping of ADM.

Landing gear down. [Figure 12-11] If the engine failure occurs prior to selecting the landing gear to the UP position, close both throttles and land on the remaining runway or overrun. Depending upon how quickly the pilot reacts to the sudden yaw, the airplane may run off the side of the runway by the time action is taken. There are really no other practical options. As discussed earlier, the chances of maintaining directional control while retracting the flaps (if extended), landing gear, feathering the propeller, and accelerating are minimal. On some airplanes with a single-engine-driven hydraulic pump, failure of that engine means the only way to raise the landing gear is to allow the engine to windmill or to use a hand pump. This is not a viable alternative during takeoff.

FAA-H-8083-3A, Airplane Flying Handbook -- 5 of 7 files (faasafety.gov)

 

[RussR]

I like the way you think RussR. Problem is there’s not always a survivable area to touchdown, and then there’s IMC and night ops to deal with also. I think it’s best to at least chair fly the critical situations.

While I do agree that it is valuable to chair fly different scenarios, I am unsure of what you’re getting at. In my mantra, if I have selected gear up, then I’m planning on continuing the takeoff in the event of an engine failure, UNLESS I have determine through preflight planning that that’s not going to work anyway. For me, since I’m selecting gear up upon a positive rate of climb, in airplanes like these, that’s, what, 20 feet AGL?

But you’re saying the opposite of that situation above, where the engine fails before you select gear up. Which means below something like 20 feet AGL. Are there really that many airports where, in this situation, it would be prudent to try to continue the takeoff, while pumping the gear up? I mean, I guess a short runway on a mesa maybe, but for virtually all normal scenarios we are likely to face, an engine failure in a light twin at 20 feet with the gear down means an instant power reduction to idle and take whatever is in front of you. IMC, night, I don’t see that it really matters. In fact, it probably makes it all the more important that the takeoff just be aborted.

 

[GRG55]

Thanks for the performance insight.
Did y’all happen teach the book response (post # 11) for engine failure right after liftoff, or the feather first technique that most of us were taught in primary training? There seems to be a large discrepancy in regards to the order of how most of us would handle this situation in comparison to the book answer. Trying to determine if the book is correct in implying that gear is more of a drag penalty than a windmilling prop??

FWIW, both grizzled veteran instructors that taught me how to fly my Aztec had hundreds of hours of time in type from earlier in their corporate pilot careers. On engine failure they both taught the same sequence: up on both the flap and gear actuators while pitching for blue line and identifying which engine. They both said being in too much of a hurry to pull back the throttle and feather the prop risked feathering the wrong one.

That seems pretty close to the book procedure.

But my plane has pumps on both engines, so the presumption is one is unlikely to need to pump the gear up by hand. Just hit the flap and gear levers. The time to hand pump suggests perhaps a different sequence may be appropriate depending on which engine has failed?

But I agree with Russ. If it's just after liftoff, very close to the ground, and the gear retraction hasn't already been initiated, I think it's practically impossible to pitch for blue line and still stay safely airborne.

I wonder if we can draw @Ted, a former Aztec owner and as much a fan of them as I am, into the discussion?

 

[Jdm]

RussR, it sounds like I’m typically raising the gear at a slightly higher altitude than you. I normally leave it down until there’s no reasonable landing option straight ahead, but probably no later than say about 50’ish. We all seem to agree that the decision is made to continue once the lever is raised. That part was never in question for me.
My question was simple. Would the rotational speed of an unfeathered engine be enough to raise the gear, and if so how long might it take? I think that has basically been answered, but the general consensus was that I should be more worried about feathering the prop than raising the gear in this situation. I get the logic. I’ve read every multi publication that I know about. The drag of a windmilling prop is enormous. The problem here is it’s not what the POH says to do in the given situation, which must be at least a possibility being there is a procedure for it. You said there aren’t many airports that fall into this category. I tend to disagree, but what do I know. It’s just my observation. One I’ve developed during my 7,000 hours of flying (5,200 multi) but I’m the first to admit that I’m still in learning mode here.

Let’s say you takeoff as normal. You decide at some low altitude that there’s no longer an option to land straight ahead. You reach for the gear knob and about that time you shuck the left engine. You know you can’t land straight ahead. You’ve already made that decision. You also know that you can’t climb well with the gear hanging out, or perhaps the gear is partially out. The prop also needs to be feathered. Me, I’m going to fly this one straight out while reducing drag at all cost.
Can this happen? Of course it can. Is is likely? No. Should I train and educate myself for situations such as this? I certainly think so. Does night and IMC play a part? Yes, for me it does. I’m much less likely to attempt an off airport landing with reduced visibility, especially if I know the terrain is jagged, or densely populated, etc.
I’ve had one catastrophic engine failure (different airplane and long ago.) It was shortly after takeoff at 600 AGL. No big problem. Plenty of performance. I did the right stuff and then got an approach back in. One thing I learned from that situation is to chair fly often and think through every possible scenario. Much better than downplaying the likelihood of such a incident happening.

GRG, that does seem pretty close to book. Nice having two pumps on that one! I’m told the mod is very pricey???

 

[whereisrandall]

Now I'm tempted to try this at high altitude to test it. Aztec C owner, single pump, at a sea level airport. Used to teach in an F model with two pumps. I primarily do multiengine training. I know that the pump does work with the engine at idle, but I also know that's not the question.

I would be super surprised if a windmilling prop could make enough pressure to raise or lower the gear enough to lock it. And I know that the aerodynamic penalty for windmilling at 4,000 ft is that it takes good technique to keep my Aztec climbing, especially if the gear's down. 50-60 hand pumps will move one way or the other and lock it.

On another note, how many of you Aztec drivers are pushing flaps and gear levers up or down at the same time and letting the hydraulic valves work it out? I avoid doing that, but maybe it's no big deal?

 

[GRG55]

...GRG, that does seem pretty close to book. Nice having two pumps on that one! I’m told the mod is very pricey???

Mine came from the factory with the dual engine driven pumps. I specifically went looking for one with that equipment.

You'll see in the POH excerpt you showed in post #11 above that from the first 'F' model in 1976 (serial # 27-7654001) until part way through the 1978 production year (serial # 27-7854050) there was a Piper factory option to install dual hydraulic pumps. It doesn't appear very many were built that way, however.

From serial # 27-7854051 until the end of production about 3 years later it appears all of the Aztecs were built with the dual hydraulic pump system as standard equipment. Mine is a 1979, serial # 27-7954081

...On another note, how many of you Aztec drivers are pushing flaps and gear levers up or down at the same time and letting the hydraulic valves work it out? I avoid doing that, but maybe it's no big deal?

If it's an engine failure during climb out or in cruise (simulated, of course) I always raise the gear lever first and then immediately raise the flap lever.
There's no take off procedure in my POH that involves having any amount of flap extended. So the flap lever pops back almost immediately, confirming audibly the flaps are retracted.
If it were an engine failure during something like a go around with full flaps I'd keep the sequence the same, gear first, but the flaps would have to be nursed up.

I don't think I have ever put the flaps and gear down simultaneously. I will sometimes use the first 5 degrees of flap to slow the airplane down to below the gear extension speed - I am pretty convinced that first 5 degrees is all drag, no lift.

 

[Ted]

RussR, it sounds like I’m typically raising the gear at a slightly higher altitude than you. I normally leave it down until there’s no reasonable landing option straight ahead, but probably no later than say about 50’ish.

I'd like to address this point. On a twin, I don't see any benefit in keeping the gear down once you've achieved a positive rate of climb. Certainly there should be some distance between you and the ground (I've watched some twin pilots pull the gear up when I could swear the tires were still touching the ground, and end up in ground effect for a bit before flying off - eek) but the gear should be pulled up as you've established the climb. Waiting just hurts you in the event of an engine failure shortly after takeoff.

My thought is that with the engine at windmilling speed after a failure, yes, the hydraulic pump could pull the gear up, but it would take too long to be worthwhile. The Aztec (at least the one I used to own) is not particularly quick at getting gear up.

 

[Jdm]

Now I'm tempted to try this at high altitude to test it.

Good deal and thank you. It’ll be interesting to see your results if you’re able. It’d also be nice to know which actually creates the most drag gear or flaps, and if the windmilling engine would assist in raising the gear.

how many of you Aztec drivers are pushing flaps and gear levers up or down at the same time and letting the hydraulic valves work it out?

I don’t because it seems that it’s asking a lot out of the system at once, but the book says it’s ok to combine the two. It prioritizes the gear. I’m pretty sure you knew that already though. I’ve attached a pic of the hyd sys pg referencing this.

 

[Jdm]

Ted. Thanks. I tend to agree, especially on this airplane with one pump. I’ve gotten a little quicker at putting the handle up after researching this topic and thinking through the posts here. I definitely put more thought into this strategy during my last trip.

 

[Jdm]

Slightly different subject: Is anyone checking the pump during the preflight? The book mentions pumping the flaps during preflight but doesn’t give any exact procedure for how to accomplish that. Seems easy enough to try..

 

[GRG55]

Slightly different subject: Is anyone checking the pump during the preflight? The book mentions pumping the flaps during preflight but doesn’t give any exact procedure for how to accomplish that. Seems easy enough to try..

I don't know what the procedure is to check the pump on an Aztec with only the single pump, but my procedure with the dual pumps is to start one engine and then actuate gear down. If the pump is working the actuator will pop back to the neutral position (this should probably work for the single pump when the LH engine is running I would expect). At the end of that flight I shut down the engine I started first, and with the other engine still running once again actuate gear down. It's the only way to test each of the pumps separately. Next trip I reverse the order I start the engines and test the pumps - that's just a habit.

 

[Jdm]

Oh yeah we do the engine driven pump check that you’re describing. I was referring to the hand pump flap check. I should have been more clear.

 

[Jdm]

 

[GRG55]

Oh yeah we do the engine driven pump check that you’re describing. I was referring to the hand pump flap check. I should have been more clear.

I do that with the flaps, as you suggested. But I usually do in the hangar or on the ramp as part of the pre-flight process of pumping the flaps down before the walk-around. I bring them up once I have the engines running before taxiing. Just my habit.

This is a great thread. Making me think through what I do, and why, and whether it makes sense.

 

[Kristin]

Engine failure drills are typically throttles up, props up, mixtures up, gear up, flaps up. No reason to hesitate on the flaps, the aerodynamic load pushes them almost all the way up and I believe that the gear gets priority with the system so putting the flaps up does not hinder the retraction of the gear.

I am in complete agreement with positive rate, gear up! The only exception is if I am on a 7,000' or longer runway, then I might delay slightly as I have some runway to land straight ahead.