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BWIAirport
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757 Incremental Takeoff Flaps Extension?

Thu Oct 31, 2019 9:48 pm

Whenever I fly on a 757, or watch a video of a 757 takeoff, I notice the flaps always seem to be extended to what appears to be Flaps 1 position, then extended to takeoff configuration 5-10 seconds later. See 15:28 in this video: https://www.youtube.com/watch?v=hA_JohxUFt4
This seems to happen without fail on every 757 flight, yet I have never seen it on another model. Is it related to airline/aircraft procedures, or is it a technical feature of the 757 for whatever reason?
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GalaxyFlyer
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Re: 757 Incremental Takeoff Flaps Extension?

Thu Oct 31, 2019 10:16 pm

The slats need to be “in place” before the trailing edge flaps. The 727 had a gate at Flaps 2 which stopped movement until the LEDs and the small extension of TEDs were positioned.
 
Max Q
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Re: 757 Incremental Takeoff Flaps Extension?

Fri Nov 01, 2019 7:39 am

GalaxyFlyer wrote:
The slats need to be “in place” before the trailing edge flaps. The 727 had a gate at Flaps 2 which stopped movement until the LEDs and the small extension of TEDs were positioned.



The gate at Flaps 2 on the 727 limited extension of the LED’s to only # 2,3,6 and 7
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fr8mech
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Re: 757 Incremental Takeoff Flaps Extension?

Fri Nov 01, 2019 8:00 am

The trailing edge do move when the handle is moved to the FLAPS 1. You can see them move in the video you posted. In fact, the AMM tells us that at FLAPS 1 the flaps move to the 1 deg position and accomplish a little more than 10% of their total travel.

The gates on the B757 (FLAPS 1 & FLAPS 20) are to prevent inadvertent movement past those positions. The gates on the B727 are at 2 & 25. They don't limit the movement, they just slow you down. I was once told that those gates also provided an aural indication for the CVR. Not sure how true that is.
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GalaxyFlyer
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Re: 757 Incremental Takeoff Flaps Extension?

Fri Nov 01, 2019 1:00 pm

Max Q wrote:
GalaxyFlyer wrote:
The slats need to be “in place” before the trailing edge flaps. The 727 had a gate at Flaps 2 which stopped movement until the LEDs and the small extension of TEDs were positioned.



The gate at Flaps 2 on the 727 limited extension of the LED’s to only # 2,3,6 and 7


True and they unlocked the outboard ailerons.

GF
 
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BWIAirport
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Re: 757 Incremental Takeoff Flaps Extension?

Fri Nov 01, 2019 4:54 pm

What exactly is the gate protecting, and why does it apparently only affect the 727 and 757?
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BravoOne
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Re: 757 Incremental Takeoff Flaps Extension?

Fri Nov 01, 2019 5:03 pm

Hinders inadvertent flap/slat retraction.
 
DualQual
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Re: 757 Incremental Takeoff Flaps Extension?

Fri Nov 01, 2019 7:15 pm

BWIAirport wrote:
What exactly is the gate protecting, and why does it apparently only affect the 727 and 757?


All Boeing aircraft have it. The gates are at the positions for normal go around and engine out go around.
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tb727
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Re: 757 Incremental Takeoff Flaps Extension?

Sun Nov 03, 2019 2:04 am

Max Q wrote:
GalaxyFlyer wrote:
The slats need to be “in place” before the trailing edge flaps. The 727 had a gate at Flaps 2 which stopped movement until the LEDs and the small extension of TEDs were positioned.



The gate at Flaps 2 on the 727 limited extension of the LED’s to only # 2,3,6 and 7


At Flaps 2, there was also something to do....
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GalaxyFlyer
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Re: 757 Incremental Takeoff Flaps Extension?

Sun Nov 03, 2019 2:59 am

Check Pack Fans ON
 
Max Q
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Re: 757 Incremental Takeoff Flaps Extension?

Sun Nov 03, 2019 7:25 am

Also, with flaps 2 the FE should check for symmetrical deployment of those four slats on his auxiliary panel
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ClarkeKent
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Re: 757 Incremental Takeoff Flaps Extension?

Mon Nov 11, 2019 2:01 am

DualQual wrote:
BWIAirport wrote:
What exactly is the gate protecting, and why does it apparently only affect the 727 and 757?


All Boeing aircraft have it. The gates are at the positions for normal go around and engine out go around.


That’s not completely correct. The gates are at positions for:

1. Normal go around.
2. Inadvertently retracting slat or led. This isn’t necessarily engine out go around flap setting.


:old:
 
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Starlionblue
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Re: 757 Incremental Takeoff Flaps Extension?

Mon Nov 11, 2019 2:51 am

ClarkeKent wrote:
DualQual wrote:
BWIAirport wrote:
What exactly is the gate protecting, and why does it apparently only affect the 727 and 757?


All Boeing aircraft have it. The gates are at the positions for normal go around and engine out go around.


That’s not completely correct. The gates are at positions for:

1. Normal go around.
2. Inadvertently retracting slat or led. This isn’t necessarily engine out go around flap setting.


:old:


Out of curiosity, are the gates a regulatory requirement? The same balks/gates seem to exist on aircraft from other manufacturers as well.
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fr8mech
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Re: 757 Incremental Takeoff Flaps Extension?

Mon Nov 11, 2019 4:57 pm

Starlionblue wrote:

Out of curiosity, are the gates a regulatory requirement? The same balks/gates seem to exist on aircraft from other manufacturers as well.


A quick look at 14CFR25.145(d) says “If gated high-lift device control positions are provide”. The “if” suggests that they are not mandatory. But, a deeper look into the design and certification regulations may reveal some requirement.


https://www.law.cornell.edu/cfr/text/14/25.145
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Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
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Whiteguy
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Re: 757 Incremental Takeoff Flaps Extension?

Tue Nov 12, 2019 3:34 pm

[twoid][/twoid]
BWIAirport wrote:
Whenever I fly on a 757, or watch a video of a 757 takeoff, I notice the flaps always seem to be extended to what appears to be Flaps 1 position, then extended to takeoff configuration 5-10 seconds later. See 15:28 in this video: https://www.youtube.com/watch?v=hA_JohxUFt4
This seems to happen without fail on every 757 flight, yet I have never seen it on another model. Is it related to airline/aircraft procedures, or is it a technical feature of the 757 for whatever reason?


Just the system, flap 1 will go out immediately but past that it won’t deploy until the slats are fully extended. Just the way the flap system works.

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