B767/757 Flap Landings.

[cambridge]

Is any operator using the above as standard for 767/757 landings. If so, any comments or problems? How does the tail clearance vary from standard Flap 30 landings? What is Boeings view on the subject?

[Bluebird]

This subject has been covered on Pprune before.

The standard landing flaps on both 757/767 is Flaps 30. Flaps 25 is also a certified flap setting for landing, and is often used when conditions dictate, i.e. high H/W component, turbulence and the landing weight is near the maximum.

I also find that using flaps 25 when landing weight is very low, i.e. when landing a 757 PF (package freighter) with not to much load, Vref can go down to about 110 kts. Using Flaps 25 in that scenario brings the Vref up by about 5kts resulting in less pitch attitude and a greater tail clearance.

The typical pitch attitide during landing on the 757-200 is 4-6° (1° lower on the 757-300) and possible body contact with a pitch attitude of 10,5°.

The typical pitch attitude during landing on the 767-200/300/400 is about 4-6° and possible skid contact with a pitch attitude of 8°. However the pitch attitude deacreases on the -200/300 with a landing weight higher than 145 tons to about 3,5-4,5° except on the -400 where it stays realtively constant with weight at about 5°.

[Albino]

cambridge, yes the operator I work for uses flap as standard for landings on the 757\767......:D

I'm guessing you meant to ask whether operators use Flap 25 or Flap 30 for landing?

I'm sure someone else can give you a more detailed answer however...

Some operators use Flap 25 as standard for landing (although I'm only aware of this on the 757, my airline does not).

No specific problems that I'm aware of using either Flap setting. With Flap 25 you have a slightly higher approach speed therefore you will use more runway and more brake energy, not an issue, just an observation. Flap 25 also has a greater limit speed which can be useful in the event of significant positive windsheer on final to prevent exceeding flap limit speed. It puts slightly less drag (and stress) on the airframe therefore you require slightly less thrust saving more fuel, in theory anyway.

You do have slightly more tail clearance with Flap 30 although what will have a greater effect on tail clearance on the day is airspeed, C of G, and of course the pitch attitude of the aircraft.

Boeing says 'For normal landings use Flaps 30. This provides additional aft body clearance from the runway compared to a Flaps 25 landing'. However both Flap 25 and 30 are approved landing Flap configurations.

Albino

[Gvendur_Bjalla]

I also find that using flaps 25 when landing weight is very low, i.e. when landing a 757 PF (package freighter) with not to much load, Vref can go down to about 110 kts. Using Flaps 25 in that scenario brings the Vref up by about 5kts resulting in less pitch attitude and a greater tail clearance.

Bluebird, that's not correct. When using 25 flaps for landing and doing Vref+5, you always have higher pitch than flaps 30. The weight has really nothing to do with pitch attitude since speed is increased at higher weights. At correct Vref+5 your pitch attitude is the same wheather the aircraft is 55 tons or 95 tons.
25 flaps ALWAYS gives less tail clearance but of course Vref 25 is ca. 4-5 Kts higher because of different contour of the wing. When you have 20kts correction on Vref I usually find it better to use flaps 25 because of less tendence to eat up distance few feet off the runway. Ground effect is much less significant at flap 25.
Flaps 25 also saves fuel as well as wear and tear of the aircraft.
I use 25 flaps whenever conditions permit on 757.
767 is a different story. Always 30 flaps there (where I work).