Light twins - single-engine climb performance

[Bravo73]

Originally Posted by rustle

WTF is that supposed to mean?

Could it just be a spoonerism of sorts?

How about:

"At MTOW in my opinion you need to be right on the ball should the worst happen at the most critical time and it could easily catch out a rusty or low time pilot."

[FlyingForFun]

Thanks for the references and thoughts, everyone. Pilot DAR - you are, of course, correct about investigation being done on the ground by maintenance staff - but they swear nothing is wrong, and I'm not convinced, which is why I'm asking the question.

The POH certainly contains performance graphs, but I don't think (and I'll have to double-check this) they are any different between de-iced and non de-iced aircraft. The maintenance organisation tell me that they would expect a de-iced aircraft to not perform as well as the manual says because of the de-icing strips on the leading edges. That's why I was looking for something else... but it seems that this something else is not there, or if it is it's impractical for me to use anyway.

Sedbergh,

could anyone who actually drives light twins tell me what it's like these days if you lose one engine just when you've left the ground? Is it ever practised or is it better avoided?

My company doesn't allow simulating engine failures below 200'. At 200', it's no problem at all as long as you do everything correctly. If you don't do it correctly, all bets are off. (Only very recently, a student of mine went for the wrong rudder pedal when I failed an engine at 500'. It didn't take very long at all before the student lost control completely, and asked me to take over. I did - but only because a crash was imminent if I hadn't - closed both throttles, levelled the wings, back under control again. But of course that's not an option closer to the ground.)

As for being below 200', this ought to be taught in a sim, and those of my students who go on to do the IR with me all experience it. I don't usually pre-warn them I'm going to do it, although they all know the company standard pre-takeoff brief which says that if a problem occurs on the ground, or in the air with the gear still down and runway still ahead, close both throttles and land back on the runway. The majority of students, despite having just briefed themselves on what to do, try to take the failed engine into the air without enough speed to maintain control. Every single one of them crashes, and every single one of them never makes that mistake again.

FFF
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PS - Rustle, I don't know if it's just me, but I took Fuji's comment to be a typo, intended to be "it could easily catch out a rusty or low time pilot"? Edit, because Bravo beat me to it!

[rustle]

Well I'm pleased for you that you three see the "error" in that light (compliment or typo), but having had > 24 hours and multiple visits* to the site to fix it it remains unaltered.

* Everyone is visible when they're here and I have visited a few times today when FA has been around; anyone posting to a thread would normally return to it to see any follow ups.

Sorry, the question remains: WTF you on about FA?

[average bloke]

FFF,
You need to look at assumed engine failure height. IE, for an MEP, the engine is assumed not to fail below (300' I think, although it's been a while). As the engine is assumed not to fail below this height, if it does you are guaranteed jack sh*t. This will be in your ops manual among other places. After this height, you must be able to construct a +tive climb with obstacle clearance to 1500'. This info is in the POH, and is up to the pilot to determine for any given conditions.

Good job punters don't know this when they get in the likes of a chieftain!

[Sedbergh]

Gulp - it all sounds like a recommendation for big singles! It worked for Mr Lindbergh
Ok, scenario - Boeing 777 full of Sedbergh and his overweight hand baggage, mainwheels just left the deck, one engine sheds the turbine blades - does el Capitano have shut the other down & land straight ahead???? M25 here we come?

I know, wrong thread & accusations of scaremongering but just out of interest!

[Bravo73]

Originally Posted by Sedbergh

Ok, scenario - Boeing 777 full of Sedbergh and his overweight hand baggage, mainwheels just left the deck, one engine sheds the turbine blades - does el Capitano have shut the other down & land straight ahead???? M25 here we come?

If he's already in the air then he's already past V1. So he continues, sheds a bit of fuel and then lands (either where he came from or, if needed, diverts elsewhere.)

(Or, at least, that's my very basic understanding of the situation. Although I'm sure that Kit will be along in a bit to patronise me then set me straight...)

[Sedbergh]

Brav

But just because you're past V1 it sounds from other posts if you're not necessarily past Vmc?? - at least in some a/c.

I'm sure Mr Boeing has it all worked out

[Bravo73]

V1 is the decision point. If a power unit goes before this point, you stop. If a power unit goes after this point, you continue.

Unless of course, the B777 was sat at the end of, say, a 20,000ft runway. Then the captain might decide that he's got enough room to stop in. (But then you don't get many of those!)


Here's what Wiki has got to say about V1:

V1 critical engine failure recognition speed. V1 is the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff with only the remaining engines. Any problems after V1 are treated as inflight emergencies. In the case of a balanced field takeoff, V1 is the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the aircraft within the accelerate-stop distance and the minimum speed at which the takeoff can be continued and achieve the required height above the takeoff surface within the takeoff distance. In this context, V1 is the takeoff decision speed.

[bookworm]

But just because you're past V1 it sounds from other posts if you're not necessarily past Vmc?? - at least in some a/c.

I'm sure Mr Boeing has it all worked out

Mr Boeing makes exclusively Performance Class A aeroplanes. Mr Beech does not.

[Finals19]

Did some IR training in a BE76 in Canada, and single engine in the missed with 2 onboard and near full fuel provided fairly good climb performance at sea level, even in above ISA conditions. Also did some IR training in the Seneca 1 and that thing was a pig. We only practiced engine failure in the overshoot simulated at altitude, and until you got the a/c cleaned up it was pretty much at zero climb even with the good engine firewalled. That assumed you got on the pedals quick and rolled five degrees into the live engine.

JAR OPS states perf B for MEP light twins. So, requirement to clear obstacles by 50 feet (I think) to 1500' after take off and a 1000'/5nm positive gradient en route clearance requirement as well as being able to hold altitude at or above MSA.

Used to fly Piper Chieftains for Air Taxi. That thing had a VG kit on it that upped our MTOW to 7348Ibs from 7000Ibs, however I would put money on the fact that if we'd lost an engine below 400' or safe obstacle clearance height, we might have just held altitude up to about 7000 on a good day. The SE service ceiling was supposed to be 13800...my point being that performance figures in the POH are based on a shiny new test aircraft!

[Nathan Parker]

But just because you're past V1 it sounds from other posts if you're not necessarily past Vmc?? - at least in some a/c.

Not for airplanes certified by the FAA. V1 must be equal or greater than Vr, and Vr must be greater than Vmc.

[average bloke]

Gulp - it all sounds like a recommendation for big singles! It worked for Mr Lindbergh
Ok, scenario - Boeing 777 full of Sedbergh and his overweight hand baggage, mainwheels just left the deck, one engine sheds the turbine blades - does el Capitano have shut the other down & land straight ahead???? M25 here we come?

The thread is about light twins, so lets not get confused and get a load of replies about V1 etc. This does not apply to MEP type aircraft (perf B).

JAR OPS states perf B for MEP light twins. So, requirement to clear obstacles by 50 feet (I think) to 1500' after take off and a 1000'/5nm positive gradient en route clearance requirement as well as being able to hold altitude at or above MSA.

Nearly correct, except that it is after assumed engine failure height, ie 300'. My previous comment stands, that below this you are guaranteed jack.

All the comments about my twin performed ok on this or that occasion are not of any value in answering the question. FFF wants the air law side of things. He flies light twins, so knows how they perform. I have to say though that I am surprised by the amount of people who do appear to fly them without knowing the facts!

[englishal]

Ref a post near the beginning....

IF the POH states a "SE Ceiling of 3000' "then you must be able to climb at >100 fpm at MAUW to SE ceiling. If you can't then the plane is not performing (after taking into account density alt of course).

as well as being able to hold altitude at or above MSA.

What happens when MSA is 10,000'? No way will a BE76 at MAUW climb.....

[FlyingForFun]

All the comments about my twin performed ok on this or that occasion are not of any value in answering the question. FFF wants the air law side of things

Very true, AB! I do find the thread creep interesting, though, I have to admit - so long as it doesn't detract from the answers to the original question.

I have to say though that I am surprised by the amount of people who do appear to fly them without knowing the facts!

I think a lot of the posts on this thread are from people who don't fly twins, which is why there is a lot of confusion, and a lot of discussion of V1 (which does not apply to light twins, as others have said). In fact, there is so much wrong information on this thread I'm tempted to ask the mods to delete it in case anyone starts quoting things from it! Normally I'd try to correct the errors, but there are too many here to know where to start!

Anyway, thanks for all the input. As it happens, I had a chance to fly the aircraft in question with one engine feathered just the other day, and I have made a note of all the relevant numbers to compare to the POH when I get a chance. I will also repeat the exercise with another aircraft in the fleet and compare both the performance and the POH for the two aircraft. Hopefully that will give me enough data to decide whether I need to push the issue any further with my maintenance organisation.

FFF
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[Mimpe]

The anwer to your questions regarding the legal requirement is covered above - there is a legal climb requirement at MTOW but as you know the realities of situation are pretty sobering.

Practicing engine out after take off at 200' has led to deaths in Australia, and is not done.
I did my Duchess rating 2 years ago, and loaded nowhere near MTOW on a slightly warm day ( perhaps 28 deg C) at 2,300 feet I could only achieve straight and level and perhaps the most subtle of climbs ie 20 fpm.
Its generally taught that if you cannot achieve immediate control with straight and level flight at low altitude on EFATO then the glide ahead shutting down the active engine is your safest bet by far. At least the crash will have some control.

(Having never been in this situation but..) if the gear/flaps are up and with rudder authority and max/RPM in the operative engine and dead wing up/nose level, you will know immediately ( within 2-3 seconds) if you've got a workable aircraft or not.

[Pace]

The best advise I heard with light twins is that the second engine gives you more options. With more options come more choices! With more choices the option to make the wrong choice.
Part of the bad safety record of light twins IMO is the training which instead of looking at all the options with the second engine concentrate on a climb and blue line.
That maybe the correct choice in some situations but not all. Fixating on blue line climbs is the reason many get into a mess.
Most twins do badly climbing on one engine especially hot and heavy but I perfectly happy in level flight.
I can remmeber many moons ago doing a totally stupid thing of shutting down a Seneca Engine in the cruise crossing the English channel on one, starting it up and landing in France.
Ok we were at 3000 feet but the aircraft does not know that it could equally be 300-400 feet.
Loose an engine at 400 feet ? Why climb? why not stabilize things in level cruise and then edge up fraction by fraction using the trim wheel.
Most airfields you can fly low level circuits.
If they are in mountainous regions chances are you will not climb out on one anyway.
Above all if its all going pear shaped keep the thing flying push the nose over and take to a field like a single.

Pace

[AdamFrisch]

Agreed with Pace. Almost all sticky situations in single engine operations can be gotten out of immediately by reducing good engine, but this is rarely taught. Fixation on blue line is the norm.

But basically in take off scenario airplanes fall into two categories: those who's Vmca is close to stall speed and those who's Vmca is above stall speed.

In the former type, an engine failure at rotation is manageable in practice. Just lower the nose, clean it up swiftly and continue. My Commander falls into this type with a 67kts Vmca which is close to its stall speed depending on flap setting. I regularly roll her up to close to blue line before I rotate anyway, just to have a little more margin.

In the latter type, you're looking at a stickier situation unless you can very quickly transfer to a higher forward speed (ie get nose over) to get rudder authority. Unless you have enough altitude to be able to reduce good engine, which is not normally the case at takeoff, of course. There is another remedy; Don't rotate at V1, continue up above blue line before you rotate if you have rwy to do so. Might wear a bit more on your gear and tires, but could get you into a safer zone. The Aerostar falls into this later category. It has a 'dead mans zone' between V1 and blue line (can't remember exactly the number now as I don't have POH yet) where you wouldn't want the engine to fail. Blue and red line are also pretty close.

All I can say about the 520 is that she'll climb about 3-500fpm if one engine is caged and feathered at low altitudes. Once you trim out the yaw, she can fly all day like this. Climb with it uncaged, its about 1-300fpm. With it unfeathered and with gear out it's pretty much nil. There is no requirement of twins that have a stall speed below 61kts to demonstrate any climb performance at all in the FAR's.

Maybe a soft field technique would be beneficial to use for the higher Vmca types? You'd rotate as normal, but then keep aircraft in ground effect until blue line in case something would happen, but once you've reached that speed you pull back and climb away?

[mad_jock]

The Vmca is one of the worst understood issues of twin single engine flight.

Current doing battle with a particulay thick polish TRE who would imagine I imagine is quite an expert on Sep agr aircraft. Twin TP he is a bloody liability seems to think V2 makes you safe what ever you are doing.

[Big Pistons Forever]

Originally Posted by AdamFrisch

In the former type, an engine failure at rotation is manageable in practice. Just lower the nose, clean it up swiftly and continue.

I have to say I completely disagree with this statement. The problem is that all light twins will only make their meager 200 to at best 300 feet per min climb if they are at the blue line speed, with the failed engine feathered and the gear and flap up. At or right after rotation none of that will happened and it is unlikely that the aircraft can maintain level flight while all the clean up happens. Even if you can accelerating from lift off speed to blue line and thus positive climb performance will be extremely problematical as there is virtually no excess power when on one engine. My experience is that being even 5 knots below blue line will wipe out any climb performance.

IMO for any piston twin any engine failure before the aircraft is at blue line with gear and flaps up and a strong positive rate of climb means the only safe course of action is to close both throttles and land straight ahead.

Personally I follow the SIMCOM method. Your hands stay on the throttle until gear/flaps up, blue line and positive rate. After that you shift your hand to the prop levers and hold them their until the 500 foot climb power selection.
If the engine fails when your hands are on the throttles you pull them both back. If the engine fails with your hands on the prop levers you cancel teh yaw with rudder lower the nose to a 5 degrees nose up attitude, identify with dead foot, verify by pulling the appropriate prop lever to just above the feather gate and then feather. You have only one action to carry out and the aircraft will be in the best possible condition to continue.

However you still must verify a positive rate of climb. Failure of the aircraft to climb means you immediately pull both throttles back and take your lumps straight ahead.

BTW for the Aerostar I rotate at 100 kts, gear up at positive rate, flaps up through 105 kts (Vxse) and hands go from the throttles to the props through 115 kts (Vyse).

[AdamFrisch]

I'm sure you're right BPF. It has never happened to me, that's why I said in practice but should probably have said in theory. Anyway, I tend to rotate closer to blue line anyway to give myself some margin, even though she wants to fly 20kts below that.

On the Aerostar that's probably not as feasible as the Vyse is much higher, so there one will have to live with a short "dead man's" gap, at least in the interest of saving your tires and on shorter airfields. But who knows - time will tell.