Earning Your Pay

[Innuendo]

Dual yaw dampers are required and a failed yaw damper is cause for limiting flight to lower altitudes, and possibly lower Mach numbers, where the Dutch roll stability is improved." - Fundamentals of Flight, Richard S. Shevell, p.307

The B-727 had significant restrictions if both yaw dampers were not serviceable.

I can't remember precise details but I seem to remember altitude limits that were quite low with just one yaw damper.

[Mizar]

Why would one ever consider side-slipping?

Because one has no choice if they are going to do an autoland. Because the manufacturer has demonstrated that it is quite safe to do so. That does not mean that it is the preferred method if hand-flying for most(although I have done it), but to make a blanket statement that it is dangerous in a swept wing aircraft is wrong.

That is the incorrect information(lost in the fog?) that a couple of us are correcting. That's all.

If you do decide to do it, my experience was that it is best to increase the power a bit when transitioning to the sideslip as speed tends to bleed off. Likely more speed bleeds off with greater sideslip.

[DEFCON]

Moon

If you revert to manually flying the ac at 100-200ft agl, why would you change inputs and how would doing so destabilize the approach?

[Guest ACSideStick]

On a large aircraft, the moment arm distance from the center of gravity and the center of pivot is very long.

When you are sitting at the very back of the aircraft in an aircraft landing in the "crabbed" technique. The sudden swing as much as 50 feet laterally is a real pants browner.

When you land with the nose aligned, you can control the rate at which the swing occurs, making a more comfortable landing, and on the centerline every time.

Certain companies encourage the crabbed landing technique, though not mine. I have only seen it a few times in many years on heavies. It is definitely a more violent arrival.

Some of the Westjet/Ex-Canadian guys might be able to chime in here and discuss the slight caster built into the 737 landing gear. I believe it was done to improve crosswind component with the low engine on the 200s. It allowed the aircraft to be crabbed without as much stress on the gear, and not needing to drop as much wing to stop drift. I never flew one, but have followed many 37s who look like they could use an alignment.

[Guest ACSideStick]

BTW

The question about autolands and why the aircraft slip should be addressed.

The Glideslope antenna is usually located in the nose. I say usually I'm sure there must be exceptions somewhere (Mitch?).

As the autopilot flies down the glide slope, it keeps the antenna exactly on the localizer. This means the rest of the aircraft is downwind of the centerline. In a really long aircraft like a A340-600, the tail may not even be within the runway confines in a really strong crosswind, and the main gear may not actually be over the pavement.

In a normal crabbed landing, the pilot makes an adjustment ( destabilizes?) After taking over and reverting to manual landing by moving his sight position upwind of the centerline so as to have the gear touch down on the centerline.

The auto pilot cannot do this, and would result in an autoland in the grass, if the wind were strong enough. For this reason, it forces the nose to be maintained on the centerline and must slip to align the wheels.

[Kip Powick]

On a large aircraft, the moment arm distance from the center of gravity and the center of pivot is very long.

When you are sitting at the very back of the aircraft in an aircraft landing in the "crabbed" technique. The sudden swing as much as 50 feet laterally is a real pants browner.

When you land with the nose aligned, you can control the rate at which the swing occurs, making a more comfortable landing, and on the centerline every time.

Certain companies encourage the crabbed landing technique, though not mine. I have only seen it a few times in many years on heavies. It is definitely a more violent arrival.

Some of the Westjet/Ex-Canadian guys might be able to chime in here and discuss the slight caster built into the 737 landing gear. I believe it was done to improve crosswind component with the low engine on the 200s. It allowed the aircraft to be crabbed without as much stress on the gear, and not needing to drop as much wing to stop drift. I never flew one, but have followed many 37s who look like they could use an alignment.

I flew the 737-200 (T-Rex) for more than a decade and always tried to land with the wheels tracking down the runway, no crab on landing.

I am sure there were a few occasions where that didn't happen, especially in YHZ and YYT because, in the cross-wind there was always enough rudder but one could only lower the wing so far just before touchdown.

I actually tried a reduced power setting on the downwind wing one time and it worked but it was an uncomfortable feeling not having the power equalized on both engines. The reduced power could be done with the C130/CV580 cause you had props and instant power if needed but again, I only used that technique about 2 or 3 times......and wouldn't recommend it to anyone.

[Moon The Loon]

Hi Defcon: I started the paragraph with a hand-flown example. As stated by others, the autopilot commences the cross-control (sideslip) at some point on the GS (I can't remember at what RadAlt). I also recall we had crosswind limits for autolands - I think It was 10 knots. Anything greater had to be a manual landing. Perhaps because of reasons stated above - too much wing down, too much off the centreline of the mains...

So hand flying to (let's say) DA on a Cat II using the wings level/heading offset, it was this that I commented about de-stabilizing at a very low height and that it was my preference to maintain wings level until the flare/idle manoeuvre.

A comment was made about the yaw felt at the rear of the airplane. Maybe so, but if done smoothly, I would still prefer this to the very uncomfortable sideslip with the "sitting sideways" feeling in my butt in the passenger's seat!

Great discussion!

[conehead]

The Glideslope antenna is usually located in the nose. I say usually I'm sure there must be exceptions somewhere (Mitch?).

.

Boeing usually builds them into the NLG doors.

[Mizar]

Bottom line after reading this thread, just like the manual says: there are different techniques for crosswind approaches. Autoland is good up to 25 knots for my plane but heard a 1011 guy talk about 40 knots, although I don't know if that was approved crosswind or just what it was capable of.

[boestar]

The 1011 could do some pretty impressive stuff so its quite possible.

[mo32a]

How about this one.....

[Boney]

That is called a "Hard Landing". Looks like the fuselage came into contact with the runway as the oleos was fully compressed.

Ouch

[Southshore]

I've that one before but never one like it. Yikes. With the high wing and the squishy (but great) trailing link gear you did kind want to 'fly' it right to the gate.

[DEFCON]

Thanks Moon

[Mitch Cronin]

I was trying to bite my tongue.... but I guess it was just a matter of time before I wandered into one of those pockets of head-space where I just didn't want to bit my tongue anymore.... and here I am now...

I'm getting a little worried about the notion of giving huge props/congratulatory yada-yadas to pilots who should have learned those basic skills long before they earned the seat in front of a hundred passengers or so...

Good grief, I learned crosswind landings and go-arounds before I got my private licence, and I'm damned sure any Canadian pilot whose earned his spot in "the big iron" (damn I hate that term! It ain't iron fellas... it's a real thin tube of the weakest metal!)... has dealt with enough of that to make it routine.... If we need to start applauding the next gen of almost-pilots for that sort of thing, we're in bigger trouble than I would have thought!

[Seeker]

I'm getting a little worried about the notion of giving huge props/congratulatory yada-yadas to pilots who should have learned those basic skills long before they earned the seat in front of a hundred passengers or so...

Nothing wrong with noting and appreciating a skill being demonstrated but, I agree, bestowing sainthood for a properly flown crosswind approach is too much!