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Asymmetrical thurst



 
 
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  #1  
Old March 11th 08, 12:34 AM posted to rec.aviation.ifr
Jim Carter[_1_]
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Posts: 403
Default Asymmetrical thurst

Watching the videos of the heavies crabbing to a landing in high cross winds
prompts me to ask: why don't they use asymmetrical thrust instead of
kicking it straight in the flare?

Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?

Have these techniques gone the way of the steam gauges?

  #2  
Old March 11th 08, 01:56 AM posted to rec.aviation.ifr
Matt Whiting
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Default Asymmetrical thurst

Jim Carter wrote:
Watching the videos of the heavies crabbing to a landing in high cross winds
prompts me to ask: why don't they use asymmetrical thrust instead of
kicking it straight in the flare?


Too slow and too hard to manage.


Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?


Poor instructors.


Have these techniques gone the way of the steam gauges?


The first technique (differential thrust) never existed to my knowledge
and the second technique is alive and well with well-trained pilots.

Matt
  #3  
Old March 11th 08, 02:09 AM posted to rec.aviation.ifr
Mortimer Schnerd, RN[_2_]
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Default Asymmetrical thurst

Matt Whiting wrote:
Watching the videos of the heavies crabbing to a landing in high cross winds
prompts me to ask: why don't they use asymmetrical thrust instead of
kicking it straight in the flare?


Too slow and too hard to manage.



At least in a jet. The time delay involved in spooling up probably has the most
to do with it not being currently used.


Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?


Poor instructors.


Have these techniques gone the way of the steam gauges?


The first technique (differential thrust) never existed to my knowledge
and the second technique is alive and well with well-trained pilots.



I've used differential thrust before so I know the technique exists. However I
was flying something with piston engines which essentially had instant reaction
to throttle inputs. Passengers liked it better than the more usual methods
because it presented them with a more conventional view looking out the window,
hence less anxiety. When you land on just one wheel after a successful slip to
a landing, they think you've screwed up.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com


  #4  
Old March 11th 08, 02:16 AM posted to rec.aviation.ifr
Jay Maynard
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Default Asymmetrical thurst

On 2008-03-11, Matt Whiting wrote:
Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?

Poor instructors.


Interesting...because the first CFI I flew with in 15 years had me use the
exact same technique my primary instructor taught me: point it down the
runway with the rudder, hold it over the centerline with the ailerons. I had
thought that was the standard light aircraft approach to the problem.

Have these techniques gone the way of the steam gauges?

The first technique (differential thrust) never existed to my knowledge


I wouldn't expect differential thrust to be manageable with a
turbofan/turbojet because of the time lag between throttle and thrust.
--
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  #5  
Old March 11th 08, 03:46 AM posted to rec.aviation.ifr
Jim Carter[_1_]
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Default Asymmetrical thurst

John R. Copeland wrote:

"Jim Carter" wrote in message
. net...
Watching the videos of the heavies crabbing to a landing in high cross
winds prompts me to ask: why don't they use asymmetrical thrust instead
of kicking it straight in the flare?

Even in a single, why don't we see more forward slips to a landing
instead of crab, kick, and pray?

Have these techniques gone the way of the steam gauges?


You want to rethink that a little, Jim?
How would asymmetrical thrust align the aircraft with the runway?

Also, forward slips are used to lose altitude. Sideslips compensate
crosswinds.

But to answer that question anyway, neither steam gauges nor sideslips are
gone. I use both of them in my light twin, except that I try to keep my
transition from crab to slip reasonably smooth, and combined with my
pre-landing flare.



When I went thru multi training we used asymmetrical thrust a lot in
Oklahoma (cause the wind never stops) to control approach attitudes. I
hadn't thought the lag time was still that significant on the modern
turbofans, so I made a bad assumption that the technique would be
applicable to the heavies.

It's been so long now I'm not sure I remember the technique right off hand,
but I believe we carried more power on the upwind engine and banked into
the wind. We didn't have to ride the rudders like in a single engine and it
was much easier, prettier, and somewhat more stable in a crosswind.

You're right - I got my slips reversed. Side slip into the wind, forward
slip toward the runway. It's all relative to the line of travel.

I wonder what the response time is for the large modern turbofans.

  #6  
Old March 11th 08, 04:11 AM posted to rec.aviation.ifr
Robert M. Gary
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Posts: 2,767
Default Asymmetrical thurst

On Mar 10, 4:34*pm, Jim Carter wrote:
Watching the videos of the heavies crabbing to a landing in high cross winds
prompts me to ask: why don't they use asymmetrical thrust instead of
kicking it straight in the flare?

Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?

Have these techniques gone the way of the steam gauges?


Slipping has been used for crosswind technique long before crab&kick.
The crab&kick was only made possible by the invention of the
nosewheel.

-Robert
  #7  
Old March 12th 08, 02:29 AM posted to rec.aviation.ifr
Capt. Geoffrey Thorpe
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Default Asymmetrical thurst

..
"Jim Carter" wrote in message
...
...

You're right - I got my slips reversed. Side slip into the wind, forward
slip toward the runway. It's all relative to the line of travel.



The way to remember it is that the names are backwards - in a side slip you
look forward, and in a forward slip you look out to the side to see where
you are going.


--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate

  #8  
Old March 12th 08, 02:02 PM posted to rec.aviation.ifr
Kobra
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Posts: 119
Default Asymmetrical thurst


"Jim Carter" wrote in message
. net...
Watching the videos of the heavies crabbing to a landing in high cross
winds
prompts me to ask: why don't they use asymmetrical thrust instead of
kicking it straight in the flare?

Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?


I see no reason to pray. There's little difference in out come with the
crab technique or the forward slip. One you put the plane in a slip early
and keep constant control pressures thru-out your approach and the other you
put the plane in a crab, relax your control inputs and put the plane in a
slip in the last 10 seconds or so. Either the plane has enough rudder
authority or it doesn't in either situation. Neither is superior IMO and
definitely neither makes one a super pilot over the other. Seems to be
personal preference.

If you are proficient at one of these techniques you've got it covered. I
don't think that there is any situation when one of these crosswind landing
techniques is the preferred and only safe way to land over the other.

Kobra


  #9  
Old March 12th 08, 03:55 PM posted to rec.aviation.ifr
Mortimer Schnerd, RN[_2_]
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Posts: 597
Default Asymmetrical thrust

Kobra wrote:
Even in a single, why don't we see more forward slips to a landing instead
of crab, kick, and pray?


I see no reason to pray. There's little difference in out come with the
crab technique or the forward slip.




There is one reason you should always pray: the wind is seldom a constant. As
you're coming in on short final and the wind rapidly shifts, will it happen at
the worst possible time? Will it do something so violent as to be totally
unexpected and leaving you no time to recover? *That's* why you should pray.

I can recall what started as a normal but gusty landing in a Cherokee Six. I
touched down acceptably and rolled a couple of hundred feet, then found myself
flying again; only this time I was cocked into the wind at about a 40 degree
angle to the runway at an altitude of about 2 feet. I had been rolling so far
after my touchdown that I had completely relaxed; all that was left to do was
taxi. Heh heh... the wind had other ideas. I firewalled it and managed to keep
from coming down sideways. *That's* the kind of stuff that causes me to pray at
hinky moments.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com


  #10  
Old March 12th 08, 10:22 PM posted to rec.aviation.ifr
Stubby[_2_]
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Posts: 6
Default Asymmetrical thurst

A B-52 pilot told me part of the approach setup was to dial in the right
angle for the landing gear so a crab would be possible while the plane was
rolling straight down the runway.

"Kobra" wrote in message
. ..

"Jim Carter" wrote in message
. net...
Watching the videos of the heavies crabbing to a landing in high cross
winds
prompts me to ask: why don't they use asymmetrical thrust instead of
kicking it straight in the flare?

Even in a single, why don't we see more forward slips to a landing

instead
of crab, kick, and pray?


I see no reason to pray. There's little difference in out come with the
crab technique or the forward slip. One you put the plane in a slip early
and keep constant control pressures thru-out your approach and the other

you
put the plane in a crab, relax your control inputs and put the plane in a
slip in the last 10 seconds or so. Either the plane has enough rudder
authority or it doesn't in either situation. Neither is superior IMO and
definitely neither makes one a super pilot over the other. Seems to be
personal preference.

If you are proficient at one of these techniques you've got it covered. I
don't think that there is any situation when one of these crosswind

landing
techniques is the preferred and only safe way to land over the other.

Kobra




 




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