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Thread: 737 landing speeds

  1. #1

    Default 737 landing speeds

    Just curious...I approach at Vref + 5. Most of my touchdowns are a couple of knots below Vref, sometimes as much as 5 knots below Vref. I suppose my problem is slightly too much flare, but I was wondering, in the real world, is a landing that is not exactly at Vref condidered unacceptable, or is a 737 pilot satisfied as long as touchdown is within 5 knots of Vref?

    Also, could you share your landing procedures? For example, at 50 feet AGL, do you bring throttle to idle? When do you start the flare? As you pull the throttles back? At 20 feet AGL?

    Thanks for the input.

    Randall

  2. #2
    BenBen Guest

    Default RE: 737 landing speeds

    In real life getting below Vref is strictly avoided. It might not be much of a problem if you are only a second away from touch-down however, during the approach, getting below Vref is dangerous because your high angle of attack will create a lot of drag and you will eventually get on the back-side of the power curve. Even maximum thrust might not be sufficant to recover this so that only putting your nose down will help you to gain speed again - not something you want to do during approach.
    The rule for approach is: Vtgt -0 / +10.
    Vtgt is Vref + 50% of the windspeed + (if applicable) a gustfactor. The additional should be not less then 5kts or more then 15kts.

    As for the approach and flare: try to simply fly the glideslope INTO the ground. I know that this takes some guts (it took me!) if you are used to make a nice flare with a small GA aircraft but that is not the way you fly a large jet. Leave your powersetting like you had it during approach, maintain also your rate of descend and your attitude. The 737 is certified for landings up to 1000ft/min! Of course that won't be a landing that makes your passengers cheer but what good are cheering passengers if your ride through the lights at the end of the runway and go mowing the lawn?
    However, there is a technique to make a nice touch-down without gliding so far into the runway. First, make sure you don't approach too fast. Maintain Vtgt up to almost over the runway, reduce thrust slightly (!) and, if things go like "on paper", reduce from Vtgt to Vref and just about 20ft over the treshold reduce to idle thrust. At that time your sink rate will actually increase so do what my flight instructor called a "break". Just make a short, slight pull on the stick and ease back again. This will "break" the sinkrate and settle you down nicely in the touchdown markings (given that you were on the glide slope).
    But never play around with excesive flaring. You will glide way too much into the runway and 150, 300 or even 600 meters are gone easily, especially if you have been a litte bit to fast anyway. The "firm" (not necessarily "hard") landing is often the safer one.

  3. #3
    BenBen Guest

    Default RE: 737 landing speeds

    Another strategy that might help you (it certainly helps me) for a nice, stable approach within all limits is to follow a flap & speed schedule. I learn that in a 737-230 simulator during my CCC course:

    Start 20 track miles away from touchdown. Trackmiles are the way over ground that you have to fly until touchdown, including curves (not a direct DME distance).
    At 20 miles out your speed should be 210kts (minimum clean speed), flaps and gear restracted.
    Now gradually reduce speed and extend flaps and gear.
    Flaps 1, speed 190.
    Flaps 5, speed 170.
    Gear down, and flaps 15, reduce to 150kts (if you adjust thrust manually you might not need to reduce thrust much, the drag of the gear will do the slowdown).
    Flaps 25, speed 140.
    Flaps 30, speed Vtgt.
    Depending on your likeing you can configure quickly so as to intercept the GS fully configurated or, if you want to speed up the approach, wait with Flaps 15 and Gear down until you intercept the GS and then configure while continuing on the ILS. However, be fully configurated upon reaching the outer marker.

    With this gradual slowdown the autothrottle does a very good job in maintaining speed and can be left engaged all the way down to touchdown. It will automatically disengage at around 20ft AGL where upon you can pull the throttle to idle, make your "break" and touch down.

    Hope that helps you with smooth and stable approaches.

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