767 F15 and F20

[Check Airman]

Hey,

Do any 767 folks know how the 763 manages to have the same limit speeds and manoeuvring (maneuvering) speeds for flap 15 and flap 20? What gives? To me it seems like Boeing's idea of a practical joke: Put 6 positions on the handle, but only 5 positions on the wing

[mustafagander]

AFAIK F15 is a certified T/O setting for shortish fields.

When I was on the B767 I asked about using F15 on noise abatement approaches instead of F5 and speedbrake but was firmly told "we don't do that". I was never able to find out why not - it seems to make sense to me, a bit more drag and stow the boards.

Just BTW, on -300s F5 is actually F9.5 or thereabouts I am reliably informed.

[sleeper]

quote[When I was on the B767 I asked about using F15 on noise abatement approaches instead of F5 and speedbrake but was firmly told "we don't do that". ]quote

We did, and it worked fine everytime! No reason, or boeing rule, not to use it.
Must be a company thing.

[Check Airman]

I know that the flap positions are not exactly the same as those written on the detent (for commonality). If I recall, F15 is actually close to 20 degrees, and F20 is something like 26 degrees. I don't loose any sleep over this stuff, but it certainly goes against intuition that different settings have the same speeds.

Can someone elaborate on noise abatement approaches re. F5/spoilers or F15?

Thanks

[haughtney1]

I think the reason as much as anything else is commonality with the 757....as you say

As for low drag (low noise) approaches..I use flap 5,15, or even 20 depending on the variability of the Vref speed to match any expected speed/runway restriction as well as the obligatory stabilized approach criteria.

I'll only use speed-brakes to help me get to a lower Vref speed if for instance I've got a bit of a tailwind..or a thermal or two is making slowing down a bit of a pain. Failing that..sod the noise..and dangle the Dunlops

Seems to work equally well for the 757-200 or 767-300

[Tree]

I don't believe there is any conspiracy. The wing is robust and the flap/slats are very efficient so the speeds for 15 or 20 may remain the same and still have plenty of buffer factor. Some operators like to re-invent but I believe the manufacturer prefers simplicity and ease of operation.

[wee one]

There have been many threads on here re the use of flap as brakes. That is to say the use of the flap in any regime but the min manuvere for the setting is not best practice. The tendcency for 75/6 operators to use f15/20 to assist in cda approach falls into this categorey.imho
The official bumf on cdas recommends , when slowing down,the use of speedbrake( with appropiate speed /vs mintoring, remember vs will remain constant, the aim, and speed will decrease, hence the name speedbrake) . Speed brakes unlike flap or gear is flexible drag on demand which can be stowed and reused at will upto the limiting flap extension for the type. So also unlike flap or gear any over use or misjudgement can be adjusted back to previous config.
Usual speeds being 220/210 185/160 from initial to intc to 4 respectively. if you select 15/20 pre intercept/or joining loc (185) to keep rod, then to avoid the use of flap as brake then you should theroetically select ref 20 (approx 150), which would mess up the descent. If you dont set ref 20 the flap has now effectively become the speedbrake.
Basically the use of intermediate speeds and flap 15/20 is using flap as drag brakes. Do you select flap 1/5 and leave the speed at ref 80...I think not. Mr boeing put a speed brake there for a reason. Its not uncool to use it... but it is uncool to leave it out and forget

[Bullethead]

G'day CA,
In response to your initial query, although Boeing specify a 20knot increment between the various flap settings min manoeuvre speeds the actual stall speeds generally don't vary by anywhere near that amount, except between F1 and F0, where the difference is 28knots. However, you are so far above the stall speed at min manoeuvre speed for any flap setting that it isn't an issue. The actual difference between the F15 and F20 stall speeds is 3knots, which is why the manoeuvering speed is the same. All these speeds are based on a weight of 130tonnes.
Regards,
BH.

[Tree]

wee one;

Excellent point. The maintenance dept and manufacturer strongly discourage flap extension at the upper end of limit speeds. It causes premature wear and expense and is just poor airmanship. Use the speedbrakes and if that is not sufficient use the gear.

[Check Airman]

Thanks in particular to Bullethead. So what you're saying is that the 20kt jumps are just for ease of operation and less brain power? If so, I can live with that. Reducing a 3kt difference to zero also seems fair in the grand scheme of things. What's your source of this great info? I'd really appreciate having a look. Feel free to PM me if you like.

Thanks again to all.

[mbcxharm]

The FCTM for the aircraft has some nice graphs in it showing what your margins are at different speeds/weight/config. The 20kts between manoeuvering speeds is clearly chosen for convenience, but we know that as long as we stick to the correct speed that we have 25 degree + 15 degree overshoot capability.

I don't agree that flying somewhere between maneouvering speeds is using the flaps as drag, if that is what is being implied. IMO it's a means of configuring the aircraft to fly at a specific speed as required, eg. 160kts on final requiring use of flap 15 at typical landing weights on the B752 a long way from the limiting speed for flap 15 of 210kIAS.

[haughtney1]

I don't agree that flying somewhere between maneouvering speeds is using the flaps as drag, if that is what is being implied. IMO it's a means of configuring the aircraft to fly at a specific speed as required, eg. 160kts on final requiring use of flap 15 at typical landing weights on the B752 a long way from the limiting speed for flap 15 of 210kIAS.

In total agreement......you have to be at high landing weights on the 767-300 to approach anything like the flap 15 - 20 limiting speed of 210 knots. Usually the aeroplane will decelerate quite happily too 180 knots at flap 5 whilst still descending at 500fpm....then just prior to G/S intercept, the selection of flap 15/20 will maintain this speed...or allow a reduction to 160kts by simply holding the thrust levers closed. Hardly using the flaps as speedbrakes IMHO

[Bullethead]

G'day CA,

The posts following your last one have answered your further questions.

The source of my information is all these ops manuals here in my study, you see I am a current B767 pilot. If there's anything else you'd like to know feel free to ask.

Why the interest in the B767?

Regards,
BH.

[Check Airman]

Thanks BH,

Not overly interested in the 76 per se, but i just found that little factoid really strange. That being said, it is indeed a great flying machine isn't it?

[Bullethead]

Yeah, I flew the B747-400 for nearly ten years and moved to the "Sportscar" for my command and love it. It's a real rocket and I have absolutely no desire to go ultra-long haul flying ever again.

IIRC the flap speeds and actual stall speeds on the 400 were similarly arranged, the 20kts gap between each flap setting bore little relationship to the actual stall speeds.

Regards,
BH.

[zerograv]

Bullet,

In my humble opinion the B752 is far more of "sportscar" (though my
experience in 763 is very little).

"Nervous Mustang" I would the call the B752.

Zero