Crosswind landings

[Jakebud]

Jim



When the engineer tries to get a bit over zealous, I take away his coffee IV. That usually settles them down a bit!



In all seriousness, we have to remember that what we see in those videos was done on purpose! Not good for the airplane, but it has to be done.



SPIKE

 

[Jim Fulmer]

When the engineer tries to get a bit over zealous, I take away his coffee IV. That usually settles them down a bit!



It's those new guys that land in crosswinds and take the correction back out that scare me, it's like when they run under a tanker.



Although I enjoyed my instructor tour at the school house I got to see allot of stupid student stuff, makes you appreciate the Instructor Pilot... ..... they are all good and most are with Southwest now!



Yea on those vids I'd hate to see what the tires looked like! That last landing was a crazy amount of crab!



Jim

 

[Jakebud]

Jim Fulmer, you at Offutt on occasion with the E-6? If so, look me up. 1 ACCS across the ramp in the E-4



SPIKE

 

[BNH4221]

Cool vids..

A couple of questions come to mind:



1. If the aircraft lands on the one gear, will that gear straigten out the craft on the runway or does the pilot have to do it? The gear only rolls one direction, right? so I would think it would have a tendency to whip the plane straight? Is the weight of the airplane too much for it to do this?



B. In the slip/crab does the airplane have to carry extra knots? Seems like it would raise the stall speed.



Just trying to wrap my feeble mind around this.



Steve

 

[Jakebud]

Steve



I a perfect world, we would all love to land an airplane in a perfect slip, with no crab and hence no side loads on the gear. However perfect we think we are sometimes, we're not! On occasion we will land in a bit of a crab, and when the happens, the airplane will straighten itself out, pivoting on the gear. It is rather amusing when it happens. Way back when, the T-38 I flew at pilot training was actually designed to land in a crab, with the consequent side loads on the main gear at touch down. It worked every time.



I can only speak for what I have flown, that being the T-37, T-38, B-52, B-1 and E-4 (747-200), but in none of those airplanes did we use an additive for a cross wind. In the E-4 we use as an additive half the headwind component, and the full gust factor. Lets say the winds are down the runway at ten knots, gusting to twenty. In that case, I would add five knots for the headwind, and ten knots for the gust component.



Of note, the B-52 lands in a crab, but uses a cross wind crab system to pivot the gear based on the cross wind component so that the gear will track straight down the runway.



Ping me at -- email address removed -- if you would like to chat more!



SPIKE

 

[TxDieselKid]

That was awsome!!

 

[Jakebud]

Why thank you! I have learned a little bit in the 22 years I have been flying!



SPIKE

 

[Vaughn MacKenzie]

A couple of questions come to mind:



1. If the aircraft lands on the one gear, will that gear straigten out the craft on the runway or does the pilot have to do it? The gear only rolls one direction, right? so I would think it would have a tendency to whip the plane straight? Is the weight of the airplane too much for it to do this?

I think what is happening is an airplane has a high polar moment of inertia. . . it takes a lot of energy to make it spin on its axis (turn left and right) and so it's not going to rotate quickly by the tires touching down. So when the plane is moving one direction and the tires are pointed another, the tires are going to slide sideways until the plane comes around. Also I think when the landing gear is making initial touchdown most of the weight of the plane is still borne by the wings, so that's why the tires slide.



Just my novice theory anyway. . .



Vaughn

 

[Jakebud]

In regards to side loads on the landing gear, I have never seen anything published as to the geometries involved, but from a "I have been there" kind of deal, it is not as if the gear is touching down anything near to perpendicular as regards the airplanes flight path. There is a side load, but for the most part the gear is still moving forward, and hence the tires will spin up at touch down.



SPIKE

 

[loncray]

Man, those videos brought back memories! A friend of mine was going up with an instructor to do touch and goes in a little Cessna - dunno the model but it was like being in a flying VW Beetle - the original one! He invited me to come along and I said "Sure!" I'm not a white-knuckle flyer in an airliner, but he was crabbing that little thing sideways onto the runway every time - and I was petrified! I kept expecting us to go into a barrel roll down the runway, leaving little bits of aircraft and body parts all the way to the end.

 

[BNH4221]

There is a side load, but for the most part the gear is still moving forward, and hence the tires will spin up at touch down

Must make for a heck of a lot of wear on the tires!



Another inane question - I read somewhere that the act of the tires spinning when they contact the ground causes the thrust reversers to activate. Any truth to this? I always assumed they were pilot activated.



Back in the day, I did some flight training in a C172. Not enough to get my ticket but enough to be dangerous. Then my wife had the brilliant idea to have a baby and then another and, well, there went that career choice...

Perhaps someday I will climb back in and finish what I started.



Thanks for the info. I'll file it away and dazzle someone at a coctail party someday.



Steve

 

[NPloysa]

Another inane question - I read somewhere that the act of the tires spinning when they contact the ground causes the thrust reversers to activate. Any truth to this? I always assumed they were pilot activated. Steve

Close, Steve. Some aircraft have squat switches which allow the thrust reversers to be activated but the pilot still has to bring the throttle levers to idle, then to thrust reverse detent. They can then add thrust to close to full power for reversers.



In other words, in flight, the pilot can activate the reversers, but without the squat switches switched, they won't work. When they land, the switches will be switched, but still nothing happens until the pilot decides it's time for them to open. (There are petal, cascade, and clamshell reversers in use today, depending on aircraft and engine manufacturer).



These switches came into practice after a 757 and other aircraft had reversers activate in flight, causing crashes.



The 707 I believe, can use reversers in flight to act as speed brakes since it is so aerodynamically clean.



Nick

 

[PC12Driver]

I could be completely wrong, but I seem to remember seeing a description of that video somewhere else saying that they were conducting autoland certification for zero/zero (can't see) approaches. That's putting a lot of trust in your equipment. And a good reason to not buy serial number 1 of an airplane.

 

[Jakebud]

Regarding PC's thoughts, if it was autoland certification, that would explain landing in a crab. The 747 I fly can autoland, and it does so in a crab. However, there is a 10 knot cross wind limit to do that. The landing in those videos appear to have a good bit more than 10 knots of cross wind however.



On the 747, the reversers will not unlock until there is weight on the gear. When that happens, you pull on the reverse levers, the reversers then unlock, and when the green reverser operating light comes on, you can get full reverses. The E-4B (747-200) I fly has GE Cf-6-50s on it, and in an emergency you can use the reversers all the way to a stop, though we usually have them stowed by 60 knots.



We have a few C-5 guys in the squadron, and if my memory is right, those guys could use idle reverse in flight on that thing, but don't quote me on that one.



SPIKE

 

[Jim Fulmer]

My guess looking at your location that you fly the E-4 correct?



Jim

Regarding PC's thoughts, if it was autoland certification, that would explain landing in a crab. The 747 I fly can autoland, and it does so in a crab. However, there is a 10 knot cross wind limit to do that. The landing in those videos appear to have a good bit more than 10 knots of cross wind however.



On the 747, the reversers will not unlock until there is weight on the gear. When that happens, you pull on the reverse levers, the reversers then unlock, and when the green reverser operating light comes on, you can get full reverses. The E-4B (747-200) I fly has GE Cf-6-50s on it, and in an emergency you can use the reversers all the way to a stop, though we usually have them stowed by 60 knots.



We have a few C-5 guys in the squadron, and if my memory is right, those guys could use idle reverse in flight on that thing, but don't quote me on that one.



SPIKE

 

[BNH4221]

Nick and Jakebud -



Makes sense to me. Thanks for the info. Wasn't it the Lauda flight in Gander that had the reversers activate in flight? Tragic. Figured there had to be some safeguards in place now.

The 707 I believe, can use reversers in flight to act as speed brakes since it is so aerodynamically clean.

Nick -

Did you ever see the video of the test pilot for the 707 that performed a barrel roll on a demo flight? I saw it on TV a while back. Completely awesome! IIRC, he knew it would do it and performed the maneuver without telling anyone. Amazing stuff.



BTW - This HAS to be one of the most interesting threads I have ever come across. What a blast!



Steve

 

[Jakebud]

Jim Fulmer



That would indeed be correct! I would suspect that we have crossed paths over at Campisi on occasion! Send me a PM, I would love to meet you on your next trip up my way.



Steve



As I recall the Lauda incident, it was a 767 that had a reverser open in flight. In theory, that is one of those, it should never happen deals, but as we have seen, it has. We practice that happening in the sim, and it can be rather violent. The throttle in question would slam to the aft (idle) stop, and then the reverser would do its thing. Should that happen, we have to shut that motor down immediately. In theory, with no other compounding problems, the airplane should be flyable. With that in mind, I have no desire to test fly that scenario though!



SPIKE

 

[HEMI®Dart]

I found this vid searching Google:



http://video.google.com/videoplay?docid=-1309610693318372088

 

[Jakebud]

That is an amusing, and realistic piece of video. There is some old video out there, of that same thing happening behind a UAL 747 out in San Francisco. The engines in the video shown are GE CF-6-80 series. We carry GE CF-6-50E2s that can develop up to 52,500 ppounds of thrust.



SPIKE

 

[evldsl]

Ok, sorry, but had to post this. Some of you may be getting tired of my aviation video links. I promised Crobertson1 these videos, but thought you guys would like it.



It's a 4-piece video of crosswind landings, a 777-200, 747SP (Special Purpose) and two more 777-200, the last one being my favorite. Watch for the rudder delfection!



http://www.metacafe.com/watch/39256/crosswinds/



Nick

Thanks I'm a mec for American Airlines