737-800 Short(ish) field landing

[Doors to Automatic]

A question for 737-800 pilots - if you are approaching an airport with a relatively (but not unduly) short runway (say 6500-7000ft). Would you use Flap 30 and Autobrake 3/Max or Flap 40 and Autobrake 2. What situation would you use Flap 40 and why not use it all the time?

Thanks in advance for any constructive replies.

[Devils Martini]

Well, at my company the "standard" configuaration for landing is Flap 40 and no autobrake. I have heard that other companies use Flap 30 as standard but we operate into a lot of short runways so Flap 40 is usually on the money.

At Skiathos (5341 ft), for example, it's Flap 40, MAX autobrake every time as standard and the same at Samos I think.

Flap 30 usually comes into play when the Vref for Flap 40 falls below 140 knots or if it's particularly gusty (rides very well with Flap 30). In this case autobrake is often used, 2 or 3 - 3 always when wet regardless of flap setting. Would consider flap 30 no autobrake on a long runway at low weights, less draggy, saves brakes, but everyone has their own methods.

In your example in particular I would expect to use Flap 40 and autobrake 3 as the runway isn't amazingly long and I would prefer to get the aircraft slowing down asap. MAX autobrake is pretty hard going on the brakes and fairly uncomfortable for all on board so usually avoided unless operationally necessary.

Does that help??

DM

[Doors to Automatic]

Thanks for your reply DM - the info is very helpful.

[calypso]

Some reason why most operators do not use flap 40 all the time (landing distance not an issue) is because it increases wear on the flaps, makes more noise and in gusty conditions you may get the flaps blowing back to 30 through the automatic flap protection system.

Autobrake max is quite agressive so only used if really necesary, not that comfy for the pax.

I would think a 6000' runway would be flap 40 and autobrake 3 plus some reverser if either wet or a short turnaround to follow.

Remember that if at the planning stage you should be able to stop in aprox 60% of the available runway, this means that in reality you should be able to use autobrake 3 and use the whole runway.

[Jinkster]

Autobreak 2, Flaps 40

[Kit d'Rection KG]

Flap 40, autobrake 3. Don't muck about on short(ish) runways - especially in the -800!

Flap 40 is preferable as the additional drag places the aircraft into a more stable part of the L/D curve and requires higher N1 and therefore much better engine response. The -800 is very unstable in speed at flap 30 at about Vref+5, and worse at +15 or so. I seldom land flap 30, and only when there's a reasonable amount of runway and a decently stable day. Of course, in strong winds, flap 30 is necessary to avoid problems with flap load relief.

The flap system is much more susceptible to wear at high speeds than low - hence it's wise to select each stage at maneuvering speed plus 10 or less, and never near the limit (unless you want, in a few years time, to really get up close and personal with the flap non-normals!)

[alexban]

flaps 40 (if wind is not a problem) ,autobrake 2 followed by manual braking plus full reverse.