"I would love to take credit for coming up with this ingenious method of approach style to reduce pilot workload, I however can not. But like you, I would love it if someone would show me and everyone else here a valid reason why differential thrust for landing should not be done. It is an aerodynamically safe maneuver for which I have never read an accident report stating, "differential thrust," as a cause."
shdw

As many have stated here, the valid and accepted reason is that it is not a recommended or authorized technique in any large jet. The reasons are many, but the bottom line is control both during and after touchdown.
I suggest you write Boeng and let them know of your opinion, perhaps they will hire you as a consultant. Perhaps not.

Sorry, but in that video a crab is carried into the approach and then partially removed to a wing low touchdown in almost every example. Some aircraft can't land in a crab or partial crab. None of them can roll down the runway in a crab, at least not under control or for very long.

 

Accepted, obviously, validity has yet to be proven. What reasons?

There isn't a single procedure that you commuter guys do that isn't written in your manuals? That is what you make it sound like if the valid reason is that it isn't in the manual.



Doubtful, but even if they were willing to I wouldn't work for them, too much politics involved with that sort of thing.

I am of the test it and experiment thinking, not the talk it over for 15 years to put out what will inevitably be found incorrect and changed by future generations.

 

At this juncture, we must label you as "highly advanced" and bow to the future of aviation. Most of us don't get paid to be test pilots, in fact we are given penalty points for experimentation in "advanced aerodynamic theory".
Please feel free to share your version of how things should be in the future.
We are all waiting for what is coming, ready to throw out the old for the new.

 

Well my reasons were strictly due to personal preference:

I preferred not to be laughed at by the other pilot.
I preferred not to apologize to the passengers.
I preferred not to be slapped by the flight attendants.
I preferred not to report to Atlanta for re-training.

But that's just me -- de gustibus non disputandur.

 

It would begin with people being receptive to new information instead of shooting it down for no logical or legitimate reason. Sarcastic, belittling individuals, we can only hope natural selection eliminates that someday.

 

YES YOU HAVE ... ME !!! I've said it only 4 times now. And let me explain it ONE more time. (If only I could draw a force vector diagram here).

You said earlier, you pull the DOWNwind engine. Yes, the crabangle is going to change (decrease). However, you just upset the once balanced horizontal force component vectors. And for every action, there is a reaction.

Here comes your reaction. Since you pulled power on the right engine, some of that thrust (pointing to the left) kept you on centerline. When you reduced it, the crab angle decreased, which means the engine thrust horizontal component that was pulling to the left of centerline, also decreased. The net effect is that you now start drifting. Since aircraft aren't designed to handle side loads, landing in a drift is not good.

Another reason why landing crabbed is bad. In every aircraft I've flown, TRs were only taken into account during aborts and abnormals. Normal landing distances were never predicated on TRs. Regardless, if you landed crabbed into the wind, and you pulled the TRs, you are in for a rude awakening. The thrust vector for the TRs in a crab is backwards pulling you DOWNWIND. And as such, causes you to slide off the runway downwind. That is why, in every aircraft I've flown with TRs, there was always a warning about closing the TRs if directional and/or drift control could not be maintained.

In the video you attached, those aircraft are being CERTIFIED at their MAXIMUM CRABBED LANDINGS ... some of which used a forward slip maneuver to align the nose just prior to touchdown. In case you didn't know this, Boeing publishes crabbed and uncrabbed crosswind limits for their aircraft. They also publish the max demonstrated and theoretical. Operaters can choose which numbers they want to use. But if they always land crabbed, they're going to go through tires and landing gear at a much much faster rate ($$$$$$$$$).

I'm not receptive to your technique because I think it is FLAWED. I'll agree, you are going to decrease your crab angle, but you're going to drift. So how do you counteract that? More wing down into the wind?

 

Many members of this forum have extensive turbine experience, and in particular, landing > 15,000lb aircraft in various crosswind conditions, including those of whom engaged in this discussion. I have personally been wrong about several things (especially pertaining to crosswind landings) and otherwise did not come out looking so well - I encourage you not to follow in suit.

 

I thought we were playing follow the leader? Dammit...

As for your other post, I will read that tomorrow when less drunk and reply then, good night.

 

...


With all due respect, why are you trying to explain what you admittedly don't understand?



You even up engines thrust along with use of rudder to center the aircraft before final touchdown. Not that this really matters since the drift you are referring to is countered by the crosswind, that is the designed purpose of this technique. Give the aircraft drift into the wind to avoid drift from the cross wind, hence needing less of a crab angle.



No, they were just a compilation of high crosswind landings. The original search was for certification, the search for that video was just high crosswind landings, not certification.



Landing one, left to right xwind, right landing gear hit first with no slip.
Landing two, right to left xwind, left gear hit first with no slip.
Landing three, left to right with left gear hitting first, small slip.
Landing four, right to left with both gear at the same time and no slip.
Landing five, right to left with left hitting first, no slip, pro verse roll.
The last 2 were go around.

1 in 5 put a partial slip into the wind during landing. The others likely had a small effect from pro verse roll leading to the a slight bank away from the wind just prior to touchdown.



On a completely different note, wasn't there an aircraft designed with rotating landing gear so it could land sideways? I think I remember seeing something like that on TV long ago but am unsure.

 

Oh my God I can't stand this.

IF YOU PULL THE DOWNWIND ENGINE ... which is what you STATED numerous times before, you will, and I repeat, WILL drift downwind, unless you counter this with some other type of input.

If the wind is from left to right (left crab into the wind), the downwind engine is the RIGHT ENGINE. If you pull the RIGHT engine, aircraft yaws to the right (decrease in crab angle INTO the wind) because of the higher thrust on the left engine, the horizontal thrust INTO the wind is reduced (because the aircraft is now at a lesser crab angle), and as a result, you DRIFT to the right.

In fact, the direction is indifferent to the overall situation at hand. If you are flying straight and level, and you pull the right engine, the aircraft will roll to the right and drift right. The SAME thing is going to happen to you if you are crabbed into the wind.

I fully understand that you are talking (typing) out both sides of your mouth.