Crab to Side-Slip for landing

I_WANNA_BE_ATP

I_WANNA_BE_ATP

New Member
It was been very windy down here in Daytona the past few days. The other day I was landing in a Piper Arrow with my instructor and the winds were 270 17kts Gusting to 22. After getting alined with the centerline of 25R at DAB, I started a side-slip, I was about 3-4 miles out at this point. My instructor tells me to keep a crab in until just before I flare. He said when I get to flying big jets, that the people in the back won't like the wing low feeling.

I have 2 questions:
a) Was I wrong for starting a side-slip out so far? I feel that I would have been stabilized for the approach.
b) What do the airline guys do??? Is it part of the profile to do one style of approach then the other or is it left up to the PF to decide how to fly the approach ?

Thanks
 
I_WANNA_BE_ATP said:
I have 2 questions:
a) Was I wrong for starting a side-slip out so far? I feel that I would have been stabilized for the approach.
b) What do the airline guys do??? Is it part of the profile to do one style of approach then the other or is it left up to the PF to decide how to fly the approach ?

Thanks
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Disclaimer: I am not an airline pilot, and what I say here is only what I have heard.

A) No, it's a matter of technique. There are thousands of ways to fly an airplane, and occasionally you'll do something different than someone else.
B) My understanding is that the sideslip isn't liked much by passengers because the plane is uncoordinated, which gives you a bit of a sideload and will move your stomach. But hopefully someone else can confirm/deny this...
 
I also am not an airline pilot but have some corporate experience.

My dad taught me this philosophy when it comes to flying techniques.
a) Safety is your #1 priority
b) Stay within comfort zone when encountering challenging conditions (this is not the time to experiment with different techniques)
c) Smoothness is next godliness.

I tend to agree with your instructor, 3-4 miles is an awfully long way to fly uncoordinated when you could just maintain a crab until the flare. Forget about the people in the back of your big jet, if you had your mother in the back seat of the Arrow and you suddenly transitioned from coordinated flight into a slip she would start to wonder what's going on. Flying is scary enough without introducing weird accelerations into the equation. So it would be far kinder on passengers to wait until maybe crossing the threshold or even in the flare to start your slip.


To answer your first question, maybe 3-4 miles is a bit of an overkill. That's 3-4 miles that you'll have to be working the rudder pedals. If you're into exerting lots of energy to fly that's cool. I on the other hand like to make my flying as easy on myself as possible.

Best of luck on those x-wind landings. They're the most fun landings to practice.
 
Disclaimer: I aint no airline pilot either :p

There are pros and cons to each crosswind technique. The pro to using the crab and kick method is that you can handle a much higher windspeed and angle due to the fact that the airplane is lined up with the runway at the very same time it contacts the runway. The con to the crab is that you really don't get to tell if you run out of rudder, and that it is a pretty quick transition from a crab to contacting the runway. The pro to the side slip method is that you can immediately tell if you have enough control authority to cancel out the crosswind.

The con to the side slip method is because yawing motions are felt at a greater level behind the center of gravity, it is uncomfortable for the passengers. The other con to the side slip method is that it can make your leg tired in a hurry. But when it comes to a safe landing or my passengers comfort, I will take safe anyday, while doing my best to make the passengers comfortable.
 
Technique varies, but the official method for the MD11 and DC10 is to transition from a crab to a side slip at about 300' AGL. I see nothing wrong with what you are doing, though.
 
I usually crab until I'm about 50 feet AGL and smoothly make the transition to a wing-low sideslip as I reduce power and begin the flare. (Remember I fly 3400 lb max gross composite singles for a living, not heavy iron.) Before I was absolutely comfortable with the maneuver or when I'm flying a new airplane model that I'm not yet 'one' with, I would typically make the transition a little earlier. That gave me an extra few seconds to figure out just how much alieron and rudder were needed for the situation.

As an instructor, the only time I would teach my students to maintain the wing-low method for an entire final approach was when they were learning the technique in the first place. Once they understood how to accomplish the task, I preferred that the airplane remain coordinated whenever reasonably possible . . . but that was just my opinion. There's nothing wrong with holding the slip for a 3 or 4 mile final, but it might not be preferable to every pilot or passenger.
 
I'm with PhotoPilot on this one. I will say that I've put in the slip a mile or two out when I've had to go around because of crosswind conditions. It's obvious that I misjudged the situation on the first approach and had to go around for it, so on the second approach I'll setup into the slip WAY early so I can figure out a lot sooner what needs to happen to land the aircraft. This also allows you to figure out whether you're going to run out of rudder when you're not 5' above the ground.
 
I taught crosswind landings to lots of students ( >1000 dual given).

When teaching crosswind landings early on I would have them depress and hold a given amount of rudder at the approach speed to show them roughly how much rudder it will eventually take to keep the long. axis aligned w/ the RWY. Then keep the aircraft lined up w/the RWY w/ the ailerons.

3-4 miles out is a pretty long final in a light plane...Usually you're turning about a 1-2 mile when nobody is around (standard pattern). 1-2 miles out or 500 feet above ground seems a little more reasonable when starting out. Then as time goes on you'll be more comfortable kicking it out over the RWY.

The down side to holding this crab from further out is it is uncoordinated flight. With that are the inherent dangers of stall/spin etc. You may find the need for 100 more RPM or an extra inch of MP due to the increased drag.

I do fly in an airline and personally I begin to add rudder as I pass the RWY numbers, about 30 feet up. Yes, it would be uncomfortable to hold rudder during the entire approach (for myself and the pax). Also w/the swept wing it's a no-no to fly like that.
 
Baronman said:
I taught crosswind landings to lots of students ( >1000 dual given).

When teaching crosswind landings early on I would have them depress and hold a given amount of rudder at the approach speed to show them roughly how much rudder it will eventually take to keep the long. axis aligned w/ the RWY. Then keep the aircraft lined up w/the RWY w/ the ailerons.

3-4 miles out is a pretty long final in a light plane...Usually you're turning about a 1-2 mile when nobody is around (standard pattern). 1-2 miles out or 500 feet above ground seems a little more reasonable when starting out. Then as time goes on you'll be more comfortable kicking it out over the RWY.

The down side to holding this crab from further out is it is uncoordinated flight. With that are the inherent dangers of stall/spin etc. You may find the need for 100 more RPM or an extra inch of MP due to the increased drag.

I do fly in an airline and personally I begin to add rudder as I pass the RWY numbers, about 30 feet up. Yes, it would be uncomfortable to hold rudder during the entire approach (for myself and the pax). Also w/the swept wing it's a no-no to fly like that.
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Good points, definetly.....ill be using ur advice......love ur signature....i could use more cow bell as well, lol
 
(Note: Crabbing into the wind is not uncoordinated flight...a side slip is.)

Always fly an airplane coordinated if you can. It makes life a lot easier to have this habit. Holding a slip in (forward or side depending on what you're doing) is sometimes seen as "sloppy" flying if you don't need the slip (i.e. 3-4 miles from the threshold.) Student pilots tend to use the controls to make the airplane "look" like it should. An example of this is setting up a slip during the approach to a runway..."the airplane should be straight so I will make it straight"...even though you are flying a very uncoordinated, sloppy, and if conditions warrant, dangerous approach.

Try to fly the crab all the way into the flare. If you want to get the slip in before you start to feel ground effect thats ok...especially if it is a new airplane for you.

Most airline pilots that fly jets (myself included) will keep coordination all the way down until the final power reduction during landing. I usually wait until I hear the GPWS give me anywhere from 30-10 feet to the runway (depending on the wind) to get my slip in. Big ol' boys will even land with the crab, it is not uncommon to see a 747 land with some narly side load in a equally narly crosswind.

Always try to fly a coordinated airplane from rotation to flare, it is not only the safest and most fundamentally sound technique, it will make you a better pilot. Transitioning to tailwheels, swept wings, jets, gliders...whatever will be much easier if you have this habit cemented into your brain. You will thank me for this advice during your first sim session after you are hired into a jet and you are not fighting the yaw damper for the rudders 4 miles out during a gusty 30kt crosswind. It also makes flying airplanes with more "spunk" for aerobatics easier as well.

Tailwinds!!
 
Not sure who said that it's a "no no" to fly a swept wing jet in a slip, but that is very incorrect. While a forward slip is not a good technique to lose altitude (although it will work and is safe in itself, it is bad because if you've botched up the approach that badly, you should just come around and do it right, absent an emergency), a side-slip for crosswind is not an issue.

As for the passengers, I can tell you that they don't notice when an MD11, DC10, etc, is cross controlled on final. The autopilot does it on an autoland, incidentally.

It is generally NOT considered good technique to kick it out in the flare in the big jets due to the potential for developing sink rates with acceleration rates that put the landing gear outside of the part 25 design box.

Also, while it may be possible to land the larger jets in a crab, it is very much not considered a good technique by most of the manufacturers.

I do not think that stall/spin is a significant issue here, but I would agree that 3-4 miles is too long of a final for light aircraft. I would also say that you should have no problem waiting until 300' or so to start the cross control, as that still gives you ample opportunity to restabilize yourself, especially in a light airplane.
 
Got to disagree with Seagull. 300 feet is too high to start cross controlling a transport jet. Start of the flare, about 50', is standard. You can slip the whole approach, if you want to, on a visual. I seldom saw that and it seemed like bad form to me, but it can be done.

But on any precision approach, to minimums, cross contolling at 300' wouldn't be done and certainly wouldn't be comfortable. So fly it the way you would if you were just getting the lights at 100'.
 
in the ERJ we crab and kick, usually just as the flair begins. In most transport jets rudder authority is not an issue like it could be in a light airplane. We have enough rudder authority that if we stomp the rudder to the floor on a V1 cut we'd flip the airplane over INTO the good engine.

As far as flying swept wing airplanes in a sideslip being wrong, I think I've read that, but my aerodynamics book is not where I can find it right now...
 
You can have what ever opinion that you want, but the manufacturer agrees with me, it's straight out of the FCOM.

Unfortunately, bad habits get into the mix for a lot of airline training departments, that start doing things based often on what works in the simulator, and nobody bothers talking to the flight test pilots or aerodynamicists that designed the darn airplane!

A very good case in point is the use of rudder to recover from unusual attitudes, which was taught by several major airlines (AA and UA, among others) and may still be taught by one of the regionals. I know the director of training at the particular regional refused to back off of that, despite being told directly it was not wise by representatives of all the transport manufacturers (including the one that made the little jet they operated), all of the flight test people, the FAA certification branch, etc. This was at a working group that was part of a White House Commission, which I was involved in at the time, where the focus of our group was specifically transport category loss of control accident reduction.

Again, Boeing directly recommends initiating cross controlling starting at 300' on any hand flown approach that requires it for crosswind correction. The autopilot does it a 150'. As for the precision approach, true, I wouldn't cross it up while IMC, but the manual also recommends keeping it coupled if the mins are that low. Can you wait longer? Sure, it works most of the time, but if you have a really strong crosswind it is adding a destabilizing factor late in the game. Personally, it also depends on the amount of crosswind. If it's just 5-10 kts, it is hardly noticeable, but if it's 25 kts it requires more aggressive action. I think the other factor for 300' for the airplane I fly is that it is close to that point where ground effect starts to become noticeable. Starting a slow transition to a sideslip at that point gets you fully stabilized in the side slip at about 100-150', due the our high approach speeds.

flyover said:
Got to disagree with Seagull. 300 feet is too high to start cross controlling a transport jet. Start of the flare, about 50', is standard. You can slip the whole approach, if you want to, on a visual. I seldom saw that and it seemed like bad form to me, but it can be done.

But on any precision approach, to minimums, cross contolling at 300' wouldn't be done and certainly wouldn't be comfortable. So fly it the way you would if you were just getting the lights at 100'.
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In the CRJ we don't really have enough wing clearence to keep a side slip near the ground and not strike a wing tip. I (well, I attempt anyways) keep a crap to about 20 feet (in the start of the flare) and then kick the rudder out. There is a this really bad moment some times when you realize you kicked the rudder too early and the plane starts drifting. You've got to sort of coax it back to center line while still flaring. Probably the hardest single thing in the CRJ. In a general aviation aircraft, I keep a crab until about 500 - 300 AGL and then start the sideslip.
 
Guess I'll join the fray real quick like...

The first few times I have a student in a cross wind, I'll have them use the side slip after turning final at about 300-400 FT so they can see the corrections they need to hold the centerline. The whole time I tell them that once they understand how to control the airplane like that I'm going to show them the best way (in my opinion) how to handle the crosswind..

The way I show them next is... crab until final power reduction, then use the rudder to bring the nose into the direction of motion and drop the upwind wing as needed to maintain the centerline.

It's the most comfortable for passengers in our little GA airplanes and when done right, it shows mastery of the airplane and just looks really impressive...
 
As I recall, there is not a transport aircraft out there that would allow you to get a wingtip with the amount of sideslip you need to compensate for the max demonstrated x-wind for the aircraft. Aircraft would not be certified that way. Someone is feeding you a load of dirty diaper there.
 
Gotta side with Seagull on this one. The max demonstrated crosswind should mean that you would avoid dragging a tip. I have heard, however, that some airplanes with engines under the wings are designed so that the flaps hit the ground first should something go wrong in a crosswind, in order to protect the engine. Can anyone back me up on this?
 
Spelling errors aside....

I am fairly certain that you can't do the max crosswind by dipping the wing. We are good up to 27kts, and just from feel there is NO way that that would work. If I recall we get a bank angle call out anything over 4.5 degrees of bank below 100 feet RA and the wingtip will hit the ground at 8.5. I may be off on the numbers a bit, but I think that is what the sim instructor said. Hopefully someone with more CRJ time then me can chime in...
 
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