Re: Airbus A300 flaps

From: (Robert Dorsett)
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date:         04 Jun 93 12:12:16 PDT
References:   1 2 3
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In article <airliners.1993.440@ohare.Chicago.COM> weiss@crowe.SEAS.UCLA.EDU (Mic
hael Weiss) writes:

>The strangest thing I saw was that no trailing edge flap was used on takeoff.
>I had never seen another aircraft take off without trailing edge flap.
>Granted, the leading edge slats were extended, but this seemed a bit odd to me.
>The trailing edge flaps were extended during landing.

This one surprised me, so I looked it up: you're right.  I couldn't find a 
flaps data card, but the A300 (B2/B4) flap/slat/krueger flap deployment 
schedule is:

        Lever                        Slats        TE    Krueger
        Closed                        0           0     Up
        First detent:                16           0     Up
        Second detent:               16           8     Extend
        Third detent:                16           15    Extend
        Fourth detent:               25           25    Extend

I also looked it up for the A320.  It does something similar.  When *holding*,
the trailing edge flaps retract in position 1.  When in a takeoff or landing
mode, they deploy to 10 degrees (slats to 18).  Ain't software modalities 
wonderful? (don't ask me how the airplane figures out if it's holding)

On the 707 (no Krueger flaps), 727, 747, and 757, you get leading edge device 
extension with the first trailing edge setting.  So, for instance, with the 
727, upon reaching flaps 2 (TE), the slats extend halfway (panels 2, 4, 6, 
7--there are four per wing).  When the TE flaps reach position 5, all leading 
edge devices (slats and flaps) are fully extended.  The 747 does something 
very similar.  

I would guess that this behavior might be a function of manufacturer culture.
On the Boeing planes, in normal operation, usually when the trailing edge
flaps reach specified detents, a multiple-mode valve assembly kicks into
action, thus conveying hydraulic fluid/pressure to the appropriate leading
edge device actuators, thus extending them (there are jackscrew assemblies 
to hold them in place, so none of the DC-10-style nonsense after hydraulic 
failure would apply--except maybe the 707, but in that case the fluid's 
trapped in the actuator).  Boeing's also known for sticking with what works, 
so it's under less pressure to innovate or try different things, unlike 
Airbus (this is a compliment for Boeing's safety culture, not a detraction).  

Does anyone know what Lockheed did with the L-1011?  Or Douglas?

(as an explanatory aside, on airliners, the leading edge and trailing edge 
devices have somewhat different functional aspects, but are selected through 
a single, common lever.  Some manufacturers refer to a "degree" setting, 
which refers to the trailing edge position.  On a 727, it would be Up, 2, 
5, 15, 25, 30, 40; on an A320, 0, 1, 2, 3, 4.  The latter approach is 
probably more "academically" honest, but the former more user-friendly:
"degrees" are probably used to make the pilots feel more like they're "in 
the loop", and do represent magnitude, but are otherwise relatively 

Robert Dorsett!!rdd