Poll: Calling all Multi-Engine Pilots

[Tarheelpilot]

I didn't understand calculus in college, and failed Differential Equations.

I can do the math when the AFM says I'll descend 900 fpm with the gear in transit, prop windmilling, flaps dragging, and cowl flaps open.

I can estimate how long it'll take to fix those conditions and figure out how much altitude I could lose, maybe adding a few feet so I don't have to dodge trees in the process.

Where are my math skills lacking?

Where you're compairing the profile with an without the gear. It may result in you leaving the gear down longer than beneficial. But I already said that in the last post.

It's ok if you don't agree. I could be wrong.

 

[MauleSkinner]

Where you're compairing the profile with an without the gear. It may result in you leaving the gear down longer than beneficial. But I already said that in the last post.

It's ok if you don't agree. I could be wrong.

I agree that I'm not calculating all the variables...6 seconds with the gear in transit, during which I may be retracting flaps, then feathering the prop, all of which results in destabilizing the airplane, so there's trim drag to consider...and just how close to the ground are you willing to descend during this process? I'm happy if the props don't touch...Most of the pilots I've worked with lose proficiency within a couple hundred feet of the ground during an engine out scenario, and in fact, a couple of them have accused me of trying to kill them with a climb gradient in a single-engine airplane that exceeded what they planned in the jet for an engine failure. Not to mention the fact that the owner was a pilot, and he'd be coming up front to provide distraction.

Sounds like calculus to me.

 

[Tarheelpilot]

I agree that I'm not calculating all the variables...6 seconds with the gear in transit, during which I may be retracting flaps, then feathering the prop, all of which results in destabilizing the airplane, so there's trim drag to consider...and just how close to the ground are you willing to descend during this process? I'm happy if the props don't touch...Most of the pilots I've worked with lose proficiency within a couple hundred feet of the ground during an engine out scenario, and in fact, a couple of them have accused me of trying to kill them with a climb gradient in a single-engine airplane that exceeded what they planned in the jet for an engine failure. Not to mention the fact that the owner was a pilot, and he'd be coming up front to provide distraction.

Sounds like calculus to me.

I don't understand what you're saying.

 

[denverpilot]

Word of caution: Be careful about pulling the throttles strait back to idle if you have an engine failure before gear up. You need to lose the nose and gradually pull the power back, otherwise you will drop like a rock and destroy the airplane like a couple of CFIs who tested the FAAs recommended technique and wrecked the airplane.

This is why my DPE showed a technique to actually DEMO this at altitude. It's definitely not on the PTS but he shows it to ME CFI candidates.

That flare is going to be HARD if you follow the Piper recommendation.

He'd rather show someone that before they have to do it, than have them surprised at how much they have to PUUUUULLL. The nose has to come down rather dramatically to hold airspeed and it's "all over with" in seconds. (He likes to say BANG! as he flares to level at the "runway" altitude.)

It's definitely going to be "an arrival" if you're shooting for minimum ground roll.

You see a taste of it in the training environment when someone pulls the throttles to idle before touchdown while they're still high. Both props go flat and the sink rate goes way up and if they don't flare hard it's a big whump. Usually they don't do it 100-200' in the air, though.

 

[Kritchlow]

Touching down on whatever happens to be in front of you when you lose an engine and the airplane descends while you retract flaps, feather the prop, and close cowl flaps. How long does that take to do, especially while ensuring that the flying pilot is maintaining proper control of the airplane? (The flying pilot, btw, is also you.)

Factor in some rising terrain and an unfamiliar airplane, and 400 feet goes by fast.

Yeah, I could put the gear back down from 100 feet, but if I know I'm going to touch down if an engine fails, why retract it?

You might actually outclimb that rising terrain if only you retracted the gear.

By that strategy, if taking off COS headed westbound, don't pull the gear until 16,000'...??

 

[Kritchlow]

Gear up or down off airport is a whole nuther question...that's why I posed it to Kritchlow, and probably why he didn't answer it.

I just don't believe in crashing fly able airplanes.

I didn't answer it because it was late and I went to bed.

Now... what's the question??

 

[Bobanna]

You might actually outclimb that rising terrain if only you retracted the gear.

By that strategy, if taking off COS headed westbound, don't pull the gear until 16,000'...??

Reductio ad absurdum; a useful way to (sometimes) advance an argument. It seems that there is some consensus forming that it may be prudent to leave the landing gear extended for the purpose of an immediate landing on the runway used for take-off. This decision point is reached quickly, usually, and gear retraction commits the pilot to managing an engine failure as an in-flight emergency (rather than a runway or low-altitude abort). Thus, on departure from KCOS westbound, a clean-up and blueline climb are appropriate once insufficient runway remains for a rejected takeoff.

Where this logic demands an exception might be Lincoln, NE or Salina, KS where over 2 miles of (usable) runway remain after rotation and liftoff...it's not hard to be at pattern altitude reaching the departure end: so. in that case, the gear is stowed and the plane is climbing at blueline long before that. As already noted (repeatedly), it depends on the type of multi-engine aircraft, also. Some have adequate power to assure a OEI climb from rotation onward. Great discussion, and Happy New Year wishes to all!

 

[Kritchlow]

Reductio ad absurdum; a useful way to (sometimes) advance an argument. It seems that there is some consensus forming that it may be prudent to leave the landing gear extended for the purpose of an immediate landing on the runway used for take-off. This decision point is reached quickly, usually, and gear retraction commits the pilot to managing an engine failure as an in-flight emergency (rather than a runway or low-altitude abort). Thus, on departure from KCOS westbound, a clean-up and blueline climb are appropriate once insufficient runway remains for a rejected takeoff.

Where this logic demands an exception might be Lincoln, NE or Salina, KS where over 2 miles of (usable) runway remain after rotation and liftoff...it's not hard to be at pattern altitude reaching the departure end: so. in that case, the gear is stowed and the plane is climbing at blueline long before that. As already noted (repeatedly), it depends on the type of multi-engine aircraft, also. Some have adequate power to assure a OEI climb from rotation onward. Great discussion, and Happy New Year wishes to all!

Lol!!!! Happy new year!! I'll read and respond when I'm sober!!

 

[Ryan F.]

Have had this discussion before, though not recently.

The most basic, most often correct answer when flying a piston twin is positive rate, gear up. The correct answer when flying a twin turboprop or jet, for that matter, is the same. Positive rate, gear up. But if someone were to say, "Well, in MY twin the right thing to do is to pitch for best rate before retracting the gear," they may very well have some backup in the form of manufacturer guidance.

Checklists are partially to blame for this confusion. Some simply state "positive rate / gear up." Others say to attain best rate of climb speed, then retract the gear. Others say to retract the gear when no usable runways remains. As is often the case in aviation, the lawyers often have more to say about the checklists than pilots do.

But looking at this from a practical perspective...

In a light twin, you're looking to reach Vyse as soon as possible. Especially in underpowered light twins (Seminole, Apache, etc.) leaving the gear down increases the amount of time required to achieve Vyse, so why would you leave the gear down, particularly when there's no remaining usable runway?

The corollary here is that "positive rate, gear up" can still benefit, particularly in a training environment from the addendum of "... when no usable runway remains." However, in my experience a disconcertingly large number of pilots misjudge localizer antennas, fences, trees, cars and houses for usable runway... YMMV.

But waiting for Vyse with the gear down, particularly at high DAs, heavy weights, flying sluggish normally aspirated light twins, is pretty dumb once you've got no chance of landing on any remaining runway, and flying off the airport property with the "Dunlops deployed" is just egregiously stupid. There's no conceivable benefit to waiting for Vyse in that case, and all one could possibly be doing is delaying that important safety milestone airspeed with extra, useless drag.

 

[Zeldman]

In some light twins I am out of usable runway right after rotation, so the gear comes up pretty quickly after positive rate. In other twins I am more than 400 agl before I run out of usable runway, so I'll bring up the gear when I have a noticeable positive rate.

And when I say positive rate, that is when I see the ground getting further away from me. At that point the VSI may be showing a negative rate of climb.

 

[Brad Z]

In a light twin, when I reach Vyse AND no useable runway left, gear comes up. That way any anomaly with the gear down results in a landing. Vyse comes pretty quickly after rotation in most light twins, so I'm really on delaying slightly compared to "positive rate of climb", and only slightly more for all but the longest runways.

Flipping the gear handle makes for a good demarcation point of committing to fly, versus putting the plane back on the ground.

 

[Ryan F.]

So... they teach that if you're 5 kts under best rate of climb, you are better off landing into the rugged terrain ahead?
Pretty poor airplane that gets ZERO climb that close to blueline.. What is VxSe in some of these airplanes i wonder..??

Makes no sense.

Not to mention, Vyse (blue line) is probably being referenced as a gospel airspeed from the POH... but it decreases with weight.

It's hard for me to fathom why delaying Vyse by leaving the gear down has any benefit whatsoever. In any twin I fly, it's positive rate, gear up. I don't argue with folks who say their checklist tells them to do otherwise because it's true, some mfgrs did recommend exactly that... but I believe it's their concern over liability rather than a true best operating practice.

The only reasonable modification to "positive rate, gear up" in a light twin is to wait for remaining runway to be unusable, which it often it almost immediately anyway. Waiting for blue line is a no-go in my book and I don't allow it of my students. I'm anty to suck the gear up into the wells as quickly as possible.

 

[Fearless Tower]

For those that delay gear up until 'out of usable runway', I'm curious......do you really know when you are out of usable runway? Are you calculating balanced field every flight and do you know when you have exceeded it?

There is a lot of talk about this in ME training before the checkride, but it seems to me that too many ME pilots don't actually realize how soon they are out of usable runway, particularly at the average GA airport.

I will submit that in a typical twin departing a 5000' runway at sea level, if you are higher than 50' AGL, you are out of usable runway.

 

[Ryan F.]

For those that delay gear up until 'out of usable runway', I'm curious......do you really know when you are out of usable runway? Are you calculating balanced field every flight and do you know when you have exceeded it?

Precisely. I wrote as much in my first post. I think some folks equate "the runway has disappeared beneath the nose" to "I have no usable runway remaining."

I will submit that in a typical twin departing a 5000' runway at sea level, if you are higher than 50' AGL, you are out of usable runway.

No one publishes that performance data so we don't know if it's 50', 25' or 100'... but in any case, it's a very low altitude for anything but the longest of runways. I wouldn't necessarily agree that you're out of usable runway at 50' on a 5000' foot runway, flying a typical light twin. You can probably get it back onto the runway and be in the process of braking. But you'll be going off the departure end of the runway at a fairly high ground speed and if there are antennae or lights on the departure end, it will be a very bad day for the airplane and its occupants.

Look at typical accelerate-stop figures in normally aspirated piston twins. In my not-overpowered PA30 it's about 3000 feet at MGW, SL, warm day. That's to accelerate and stop ON the runway. The amount of runway available for stopping decreases exponentially as the aircraft accelerates, and once it's airborne all bets are off as it must descend and touch down before the brakes can be used to decelerate again.

I'm a fan of keeping things simple in aviation. Positive rate, gear up. Give yourself performance and minimize the time you spend in the Vmc-Vyse window. Most of these airborne abort scenarios involve going off the runway or off the airport property altogether so the gear being left in the extended position offers limited value anyway.

Someone wrote "I'm not a fan of crashing flyable airplanes." I like that... sums up how I feel about this subject.

 

[mondtster]

For those that delay gear up until 'out of usable runway', I'm curious......do you really know when you are out of usable runway? Are you calculating balanced field every flight and do you know when you have exceeded it?

There is a lot of talk about this in ME training before the checkride, but it seems to me that too many ME pilots don't actually realize how soon they are out of usable runway, particularly at the average GA airport.

I will submit that in a typical twin departing a 5000' runway at sea level, if you are higher than 50' AGL, you are out of usable runway.

The "out of runway, gear up" discussion always grates on me, regardless of how many engines the airplane has. I've run across far too many instructors and pilots who believe "out of runway" means when they are crossing the departure end of the runway threshold. As you noted, that is not the case, and as you and others have also remarked, they may be out of usable runway at or before rotation or at best, shortly afterward. The only exception may be at an airport with a 10,000' runway.

As an interesting sidenote, I took my initial multi checkride in a B55 Baron on a 5500' runway with a field elevation of about 1000' MSL. That examiner's assertation was that if you combined the takeoff distance over a 50' obstacle and the landing distance over a 50' obstacle you could get an idea for when you'd be out of useable runway. I understand his theory, but I disagree with it somewhat because you wouldn't be in a landing configuration if you cut the throttles at 50' off the ground from a takeoff. Anyway, if you do those calculations and believe them you could theoretically land a Baron on the runway from an aborted takeoff with 5500ish feet of runway. I personally think the average, unexpecting pilot will be through the fence and off the runway, if this actually happened.

I'm a keep it simple kind of guy. All the retractable twins I've flown haven't had any flight or system characteristics that would present a compelling reason to not retract the gear as soon as there is a positive rate of climb. That's also what I teach students, as it seems to be the best practice that fits the most airplanes.

 

[denverpilot]

I think the most interesting side effect of this thread was digging deeper in the Seminole manual to see what the gear retraction and extension speed did to their recommendations.

The "positive rate, gear up" mentality guarantees a belly landing until a certain amount of time has passed, all dependent on descent rate following an engine failure.

I "get" why Piper says the leave the gear there for remaining usable runway now. The lack of power to climb out with one windmilling and lack of time to reconfigure, meant they had no better option to put in the book.

Turbo pig! Heh.