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All-engine-operative asymetrical power landing

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All-engine-operative asymetrical power landing

Old 16th Jan 2009, 02:48
  #41 (permalink)  
 
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I didn't know the Tristar could do that (automatically)! That's nice. How would it do that? If it detected a yaw in the opposite direction of a full rudder position?

It compensates crosswinds in both yaw and roll axis down to 5 feet. Additionally, DLC spoilers can compensate for pitch. All combined...

Last edited by jmig29; 16th Jan 2009 at 02:53. Reason: correction and quote
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Old 16th Jan 2009, 02:50
  #42 (permalink)  
 
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compensation

The L1011-500 with DFCC's, I mean
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Old 16th Jan 2009, 06:37
  #43 (permalink)  
 
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Pleasure fly out of an air attack base in NorCal. Guppy's comments don't align with local procedures.
Quite irrelevant, really. I fly air tankers and have for many years. It's a technique I've used in light air attack aircraft through large four engine air tankers, when required.

You attempt to persuade us that it is acceptable for those with your skill set by stating...
I didn't attempt to persuade anybody. In fact, I said I won't discuss the specific techniques because I don't teach them, and I don't think attempting to convey a technique in detail over the internet is a good idea...certainly not where someone might try to go perform that technique without adequate supervision. Get your facts straight.

Yes, but does the crosswind during take off prohibit you from maintaining directional control with rudder and nws?
Clearly so, else the technique wouldn't be necessary, would it?

I thought of this thread this afternoon as I was reviewing the AFM for a light twin, a Cessna 310Q. In this pilot handbook the manufacturer recommends the use of assymetrical thrust for takeoff in a strong crosswind. Imagine that. In fact, it states "For crosswind takeoffs, additional power may be carried on the upwind engine until the rudder becomes effective. The aircraft is accelerated to a slightly higher than normal takeoff speed, and then is lifted off quickly to prevent possible settling back to the runway while drifting."

And your special techniques are?
As stated early in the thread, not to be discussed in detail, for the same reasons stated above. READ.

I don't see how this aids directional contol. Not really sure of it's merit either if you've used no flap V1 and VR take off data, but okay, as you wish, and no further explanation requested.
You're making an assumption that a part 25 aircraft with a V1 or published VR is always the subject of discussion. You're referring specifically to the technique of applying flaps late in the takeoff. This isn't just a directional control issue, but also a rough field technique, also applicable to strong crosswind situations because when operating from rough airfields in remote locations, there may be only one runway and it may be the only game for many, many miles.

In aircraft which utilize drooped ailerons along with flaps, lowering of flaps may be useful late to protect the flaps, raise a tailwheel, or rapidly bring the airplane off the ground, and as this isn't a technique often used in normal operations, it does qualify as a "special technique."

You didn't specify your other useful techniques, but clearly you believe that with your skills it is acceptable to use assymetric thrust to aid directional control during a take off roll.
I said nothing of the kind. Put words in your own mouth. Not mine. It's hardly a matter of skill. However, if you find it unusual or out of the realm of reasonable technique, I submit it's because it's outside the scope of your experience...not because the technique is illegitimate.

How do you propose to deal with a failure of the upwind powerplant while it is your ONLY other means of maintaining directional control during an out of limit crosswind take off?

It strikes me as being obvious that if the additional thrust one one side is required to keep straight while accelerating, you are sure gonna need it while de-accelerating if you are required to abort due to the loss of your upwind powerplant.

If you can explain to me just why such practice is not a compromise of safety - and eactly how one can be assured of staying on the runway (or road or taxiway) if the upwind donk stops while conducting a take off that is reliant on the use of assymetric thrust, I promise to shut up and never post on the topic again!
Powerplants (as opposed to "donks") are a system, and a tool; they're made with variable power settings for a reason. You make many assumptions, not the least of which is that the techique is restricted to cases in which the aircraft is absolutely reliant on assymetrical thrust for the takeoff. Perhaps it hasn't occured to you that assymetrical thrust may be used to enhance controllability, and isn't only confined to circumstances in which there is no other recourse but it's use.

First and foremost, rejecting the takeoff involves retarding throttles/power levers/thrust levers. Some training and some aircraft use assymetrical reverse on a rejected takeoff. Some use assymetrical reverse during a landing to aid or enhance controllability. I do too. Where appropriate.

Now, as you brought up the scenario of a rejected takeoff with a failure of the upwind engine, in an extreme situation in which the takeoff is entirely dependent upon that upwind engine for directional control, the question you've proposed is what to do about the failure of that motor. If both engines are retarded and the downwind engine is provided reverse...then directional control is still enhanced by the powerplants...push power up on one side or pull it back on the other...still directional control.

You stated that if one needs to consider assymtrical thrust for a takeoff, one shouldn't go flying. However, we've just seen an aircraft manufacturer that describes the technique as part of the approved pilot handbook. This isn't an unknown, or dangerous, or impossible technique. Your responses suggest, as stated before, that it's far outside your realm of experience, and that's fine. Again, this doesn't invalidate the technique...it just means you don't understand it.

Clearly.
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Old 17th Jan 2009, 08:57
  #44 (permalink)  
 
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If you can explain to me just why such practice is not a compromise of safety - and eactly how one can be assured of staying on the runway (or road or taxiway) if the upwind donk stops while conducting a take off that is reliant on the use of assymetric thrust, I promise to shut up and never post on the topic again!
Good question. SN3Guppy, you used an awful lot of words but somehow managed not to answer it.
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Old 17th Jan 2009, 11:30
  #45 (permalink)  
 
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Read again, and you'll find the question was answered. To repeat the information would only mean you wouldn't understand it, twice.
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Old 18th Jan 2009, 06:23
  #46 (permalink)  
 
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Guppy, when you are in a hole - STOP DIGGING!!

It was obviously not possible for you to simply address the question I posed, so instead (as usual) you wrote an essay that danced around the subject matter, making sure that it spelt out just how much of an ace you really believe yourself to be.

You may be busy sitting in an armchair, but I happen to be busy flying for a living.

Can we leave out the invective, please ?
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Old 18th Jan 2009, 07:23
  #47 (permalink)  
 
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I just cracked the AFM for a Cessna 414...same thing...manufacturer recommending assymetrical thrust for a crosswind takeoff. Go figure.

Apparently you know more than the manufacturer.

I was busy flying a week or two ago. Now I'm furloughed...and yes, I do have the time. Your question has been answered, but nobody can force you to read, nor comprehend. That's all up to you.
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Old 18th Jan 2009, 16:24
  #48 (permalink)  
 
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I just cracked the AFM for a Cessna 414...same thing...manufacturer recommending assymetrical thrust for a crosswind takeoff.
Likewise with the 411....and 401/402 older series.
DC-3 and C-46?
Absolutely.
With the C-46 especially, if you don't use differental power (initially) during a significant crosswind takeoff, you will find yourself in the weeds...real quick.
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Old 18th Jan 2009, 16:43
  #49 (permalink)  
 
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Crosswind takeoff - jets

Training in the 747s, I never recommended such procedure...
However, one exception.
xxx
In case of strong crosswind, say from the LEFT...
I would recommend to delay power increase on nș 3 engine, until engine gets air undisturbed by fuselage.
Until say, airplane rolled some 20 knots or so... then a more careful increase to "SET POWER".
Engines downwind from fuselage (nș 2 or 3) are prone to compressor stall.
xxx

Happy contrails
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Old 19th Jan 2009, 18:54
  #50 (permalink)  
 
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Interesting debate, and so far SN3Guppy seems to have some authoritive weight on his side. I do however see the flip side of the argument, and as yet nobody has answered the question - exactly how one avoids the weeds at the other in the event of an engine failure - especially the upwind one? Surely you must need the assistance of the assymetic thrust at both ends - or is it a case of accepting some risk of an "excursion."

In many cases the option of differential braking may assist during the abort, but only if one presumes that maximum brake energy is not required. In the case of a "balanced" field, however, I would suggest that the practice cannot under any circumstances be condoned - not only would the acceleration be less than required to meet the book values, but so also would the braking efficiency.

This may go to a draw, but it will be interesting to read further.
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Old 19th Jan 2009, 21:15
  #51 (permalink)  
 
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Quite simple, and yes, it's been answered already, in detail.

Retarding the power to idle is a good start. Nosewheel (or tailwheel) steering, assymetrical braking, assymetrical reverse, as required.

Particularly where you've invoked the issue of a balanced field or published numbers: reverse isn't included in the rejection numbers (on a dry runway), just as it isn't part of the landing numbers. As assymetrical thrust is an added dimension when it comes to enhancing control on takeoff, so is assymetrical beta, or reverse.

An aircraft calculated for takeoff based on a reduced thrust or reduced power setting, which uses the upwind engine at a higher power setting for the initial roll pending rudder effectiveness (or later into the takeoff, as required) hasn't compromised the data; especially where this is a recommended technique by the manufacturer. The "QUESTION" has been asked regarding failure of the upwind engine, and it's import during a rejected takeoff. In such a case, if the upwind engine was used to enhance control pending rudder effectiveness, the issue only becomes an issue once the speed is reduced during the rejected takeoff below that of rudder effectiveness, once more.

Additionally, where an aircraft with no brakes applied might easily weathervane into the wind on takeoff, the same airplane during the rejected takeoff with brakes applied does NOT have the same tendency...any more than it weathervanes into the wind while parked with a direct crosswind and brakes set. The tendencies to turn into the wind with a strong crosswind during a rejected takeoff, vs. a takeoff, are not the same, and the ability to stop or maintain directional control is therefore not compromised.

Again, if one can push one engine up a little farther to aid in directional control on takeoff while the rudder takes effect, then one can also use assymetrical reverse (and I have done, many times before) on landing, or in the case of a rejected takeoff.

Furthermore, whereas it's a legitimate technique recommended or provided by some manufacturers, where is the argument?

A bigger issue in a rejected takeoff with a strong crosswind, particularly a gusting crosswind, may be keeping the wings level in some aircraft. This can be particularly true in some propeller driven aircraft in reverse. In aircraft employing lift-destroying devices such as autospoilers, these effects are somewhat reduced. In any event, this doesn't fall back to "is it a good idea" or "one should never consider," but back to situational awareness, and the good old fashioned practice of flying the airplane until it comes to a rest.

Remember that this part of the discussion revolves around a statement made earlier in the thread by a poster who stated emphatically that one should never consider taking off if assymetric thrust is required...and that's been fairly conclusively proven to be bunk.

Last edited by SNS3Guppy; 19th Jan 2009 at 21:33.
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Old 21st Jan 2009, 00:22
  #52 (permalink)  
 
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SN3Guppy stated:

Particularly where you've invoked the issue of a balanced field or published numbers: reverse isn't included in the rejection numbers (on a dry runway), just as it isn't part of the landing numbers. As assymetrical thrust is an added dimension when it comes to enhancing control on takeoff, so is assymetrical beta, or reverse.

You and Fully Spoolled mention balanced fields. But didn't YOU just state that reverse is not included in the rejection numbers. How therefore can you include any kind of reverse in YOUR rejection numbers, methods or criteria?
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Old 21st Jan 2009, 05:30
  #53 (permalink)  
 
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But didn't YOU just state that reverse is not included in the rejection numbers.
I see you're not familiar with the certification requirements for transport category airplanes.

Again, as stated earlier, I can go on explaining this to you over and over, but each time is just one more time you're not going to understand. It's been given more than once now. Read.
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