A technique question for the ages......

[Colonel Savage]

Why does the x-wind limit increase with the flap setting?

 

[tomgoodman]

x-wind/flap relationship

Why does the x-wind limit increase with the flap setting?

Increased flap settings allow landing at a lower pitch attitude. This can improve ground clearance in a bank. Some airplanes also provide increased aileron authority at lower speeds/higher flap settings.

 

[Colonel Savage]

Understand to first point. The second point, do any civilian types have the extra aileron authority, or is that just military types?

 

[Fly91]

Of course then there is the B-52, which I understand you do not use either technique. You crap the wheels and land in a crap, no wing down, no kick, just land looking out the side window. Any B-52 drivers care to confirm?

B-52 has rotating wheels, you crab the plane and the wheels are pointed straight down the centerline.

BUT......The T-38 Talon, which I flew 4 times (incentive rides in AF ROTC)......is truly a plane that you don't crab or cross control..
You come in, wings level, regardless of the crab angle..and slam it on. Yup, they go through alot of tires. I'm no expert on the t-38, but our pre-flight briefing and pre-landing verbal briefing by the instructor pilots on final approach was....."do not touch the rudders on landing, feet flat on the floor."

 

[Fly91]

Increased flap settings allow landing at a lower pitch attitude. This can improve ground clearance in a bank. Some airplanes also provide increased aileron authority at lower speeds/higher flap settings.

I see you flew the T-38.

What is it called on the Talon that doesn't let you use rudder on landing. It was back in 1992 when I got a few rides but I can;t remember what they called it. I assume its like other aircraft where you just get too much deflection.

?

 

[Colonel Savage]

"What is it called on the Talon that doesn't let you use rudder on landing?"

Rudder limiter? But sounds like the T-38 is opposite from most jets I'm familiar with, as most systems limit the rudder travel at higher speeds (such as after flap retraction), not lower.

 

[LR25]

Done both on 747, seems to work out whether you crab or cross control. If strong wind, you can cross control, but have to watch lowering the wing too much, but thats seems normal on most airplanes.

 

[tomgoodman]

T-38 & rudder

Col Savage & Fly 91,

It's been a long time since I flew it, and you can probably get a better answer from an active T-38 IP in the Military section of the forum.
The only use I made of the rudder was to keep the airplane tracking straight down the runway during takeoff or landing roll. (A button on the stick engaged nosewheel steering, but that was much too sensitive for anything above taxi speed.) The "crab-only" technique was used for crosswind landings. One reason was that inflight rudder application would give you a substantial roll (360-degree rudder rolls were demonstrated at altitude), so students were indeed told to "keep their feet on the floor" until rollout. Sideloads from touching down in a crab were moderate, perhaps because the T-38's tire footprint was small.

 

[Fly91]

"What is it called on the Talon that doesn't let you use rudder on landing?"

Rudder limiter? But sounds like the T-38 is opposite from most jets I'm familiar with, as most systems limit the rudder travel at higher speeds (such as after flap retraction), not lower.

Thats the weird part. There is no "rudder limiter", you get full deflection at slow speeds...thats where the problem happens if you use rudder during landing. When I flew the 747 it was a high-speed issue with a system failure. That had a rudder limiter above 300 kts IIRC, so rudder travel would be limited.

The T-38 was strange because it was a low speed issue.

 

[Fly91]

Col Savage & Fly 91,

It's been a long time since I flew it, and you can probably get a better answer from an active T-38 IP in the Military section of the forum.
The only use I made of the rudder was to keep the airplane tracking straight down the runway during takeoff or landing roll. (A button on the stick engaged nosewheel steering, but that was much too sensitive for anything above taxi speed.) The "crab-only" technique was used for crosswind landings. One reason was that inflight rudder application would give you a substantial roll (360-degree rudder rolls were demonstrated at altitude), so students were indeed told to "keep their feet on the floor" until rollout. Sideloads from touching down in a crab were moderate, perhaps because the T-38's tire footprint was small.

Yeah, I probably did about 10 landings total and thats what I remember the most. The instructor pilots would keep saying it all the way to touchdown...so it must have been a pretty important procedure. And yes, it was just a "slam it on" for crosswind landings no matter how much the angle was. It would hit solid as a rock and straighten right out.

We were allowed to take the controls as soon as we were at 500 feet on climb out and literally fly the entire time till about 500 feet on final....then it was sit there like a statue and don't touch anything.