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Flapless B737 LDG
Hello,
In the unlikely need for a flapless landing I read in a procedures manual to choose the runway with No crosswind. What would be the considerations to go for the runway with the least crosswind, other than having the best landing distance performance? As I was taught flying GA aircraft, in the event of heavy crosswind we were to land with less/no flaps. This is reversed thinking I know, but the influence of xwind would be less on a B737 without flaps compared to with flaps just as on a C172. Thanks for the input. |
Doesn't it imply that you'll have more headwind, which is preferable with no flaps.
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From a Boeing article on tailstrike avoidance.
MISHANDLING OF CROSSWINDS A crosswind approach and landing contains many elements that may increase the risk of tail strike, particularly in the presence of gusty conditions (figure 3). Wind directions near 90 deg to the runway heading are often strong at pattern altitude, and with little headwind component, the airplane flies the final approach with a rapid rate of closure on the runway. To stay on the glidepath at that high groundspeed (figure 4), descent rates of 700 to 900 ft (214 to 274 m) per minute may be required. Engine power is likely to be well back, approaching idle in some cases, to avoid accelerating the airplane. If the airplane is placed in a forward slip attitude to compensate for the wind effects, this cross-control maneuver reduces lift, increases drag, and may increase the rate of descent. If the airplane then descends into a turbulent surface layer, particularly if the wind is shifting toward the tail, the stage is set for tail strike. The combined effects of high closure rate, shifting winds with the potential for a quartering tail wind, the sudden drop in wind velocity commonly found below 100 ft (31 m), and turbulence can make the timing of the flare very difficult. The PF can best handle the situation by exercising active control of the sink rate and making sure that additional thrust is available if needed. Flight crews should clearly understand the criteria for initiating a go-around and plan to use this time-honored avoidance maneuver when needed. |
Not much difference to normal, but significant, crosswind landings .. when one pushes off the drift to fly whatever is left to go cross controlled, simultaneously the pitch attitude has to be increased somewhat to prevent a sink rate increase .. just becomes a bit more clearance critical with lesser flap selections, including clean .. so, perhaps, better to find the least crosswind option sensibly available ?
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This may be the time for a firm landing , no crosscontroll , then rudder as needed and do not try a smooth nosewheel touchdown. Max reverse and max autobrake.
After all the crosswind vector is marginal at V ref 40 plus 70 kts, Eh John? I would think floating and rwy distance is main problem. |
Max reverse and max autobrake. Use of autobrakes is recommended. Autobrake setting should be consistent with runway length. (See Autobrakes Landing distance in the PI section of the QRH, Performance Limitations and Planning Manual or EFB). Use manual braking if deceleration is not suitable for the desired stopping distance. Immediate initiation of reverse thrust at main gear touchdown (reverse thrust is more effective at high speeds) and full reverse thrust allows the autobrake system to reduce brake pressure to the minimum level. Less than maximum reverse thrust increases brake energy requirements and may result in excessive brake temperatures. Let's say you stuffed up the flare and floated all the way to the 2000ft mark before touching down, and when you did you were ten knots fast, you'd still stop 400m before the end of the runway. On a runway of that length I'd use AutoBrake 3 and I would go around if a float looked like taking me past the 1500ft touch down marker. Obviously that is just my own opinion of the risks involved but I thought it worth mentioning that max auto brake isn't a given and (in my mind at least) should be avoided if possible at those high speeds. |
Indeed if not runway limited,max autobrake use is plain stupid.
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Framer
You are funny
Max autobrake is mandatory in this case ,flapless, Anything else is gross incompetence,,,, Practicaly ,I allways land standar F 30 auto brake 3 and squice it of when happy. I am a firm beliver in speed , energy squear root etc, but mostley I hate paperwork and the press so I stop befor runway end, always,. End. |
Hey blusdup, I think you're funny. What part of "here's what the FCTM says" didn't you understand? Don't see the word "mandatory" in there anywhere, do you?
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Blusdup,
[QUOTE]Max autobrake is mandatory in this case ,flapless, Anything else is gross incompetence,,/QUOTE] Are you just having a laugh or?:eek: |
Originally Posted by BluSdUp
This may be the time for a firm landing , no crosscontroll , then rudder as needed and do not try a smooth nosewheel touchdown. Max reverse and max autobrake.
But, how are you going to counter the rolling action of yaw without using opposite aileron? I think however we need to keep this in perspective. It will land in a crosswind but choosing a runway with a headwind with the large energy involved will be preferable. Command stuff... |
Obviously has his own manual printed.
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Blusdup
You are funny |
Flapless B737 LDG
Since all non normal landing distance calcs assume max manual braking. No data provided for less.
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Yip. What's the relevance though?
Boeing suggest AutoBrake commensurate with runway length in order to prevent exceeding brake energy limits. They certainly don't want you to use max for all non normals just because they haven't provided the data. If that was the case we'd have Boeings blowing fuse plugs every day. |
Since all non normal landing distance calcs assume max manual braking. No data provided for less. You use the AB 2 column first ,if not enough margin use AB3 ..... Not brain science really... |
Are the corrections for landing distance linear?
Energy to be dissipated increases with the square of the speed don't forget. I would suggest that using the QRH Normal landing distance figures to extrapolate to Vref40+70 would not give you an accurate answer, and you have know knowledge in which direction the error is. I would class that as "brave" behaviour personally. "So, Bloggs, with the QRH non-normal distance there why did you invent your own landing distance calculations?" |
De Facto: why would you use the normal configuration landing distance if you have clearly a non normal.
why would you use the figures for XXXm/5kts above Vref when Boeing gives you the figures they calculated in the exact non normal configuration you are in. And the NON-NORMAL landing distance table says those distances assume max manual braking, we use max autobrake because then the brakes will be applied sooner after touchdown and take over manually straight after. When you have a non normal you don't have to think about brake energy, these figures are approved by the FAA and JAA so why would you use anything else? |
de facto:
add the SPEED INCREMENT above VREF, you are using all flaps up the it should be about vref40+50kts Jwscud: Are the corrections for landing distance linear? using the QRH Normal landing distance figures to extrapolate to Vref40+70 would not give you an accurate answer Although the distance from the Normal Landing Distance tables should never be used, it does give you a good starting point. But only for instance by comparing the additive (difference) for Normal and Non-Normal Max Manual Braking as published in BOTH Normal and Non-Normal tables. This must then not be used as factual but can be used as a guidance on an indicative increment requirement. It could indeed be professionally sound to adjust Max Manual Braking with a lesser Autobrake requirement if runway length allows, most airfields we fly into do not have 3400m available to them, if you do operate into those lengths, then use a lower setting but with caution as no guidance exists on them. Finally, it may be a good idea to have in your mind the deceleration rates for auto brake settings, allowing thus for a rough distance calculation to be made based on any touchdown speed. This rate is what is achieved by auto brakes and is modulated to be achieved, by adding/removing brake pressure due to other stopping factors such as reverse (primary), drag and friction. |
737-800, max landing weight at 2000' PA, 5650' with a 15% margin and 1,000 feet of air distance from threshold. Actual stopping distance is around 3,800 feet. This is flaps zero at VREF 40 + 55.
Why you would arbitrarily throw max brakes into that situation is beyond reason. Just a good way to ruin a set of brakes, tires, and possibly axles. Our QRH makes no mention of crosswind, and states "brakes consistent with runway conditions". |
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