Re: Squat interlock

Date:         27 Aug 99 14:03:39 
From:         Ernie Fidgeon <>
Organization: MBnet Networking Inc.
References:   1 2 3
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JF Mezei wrote:
> "David R. Hendrickson" wrote:
> > Take Off Warning, Ram Air inlets, the NextGen's overwing hatches...lots
> > of systems look at the air/ground condition of the aircraft...
> I am very curious about overwing exits being made conditional of the squat
> switches. What happens when a plane lands on its belly with gears not
> retracted ? (or if gears become detached from the plane) ? ? ? ? Does this
> mean that overwing exists will not function ?
> I would have thought that cabin pressure alone was sufficient in preventng
> them from being opened during flight.

If I recall the FARs correctly, the overwing exit must function alone.  Any
system that could crap out and fail the overwing is a no-no.

Secondly, most overwing exits are mechanically actuated with a sensor for
telling the flight crew of a seal breach prior to takeoff, and to verfiy
arming of the slides.

Third, most exits operate by removing inwards as the fay surface (or overlap)
is on the inside.  IE- the door is bigger than the cutout just like the
windows so the cabin pressure acts to force the door closed against the
airframe, physically preventing "opening" while pressurized.

Reference of the Next Gens overwing door to the air/ground parameters may be
for pilot reference only(?) or to somehow link it to the offwing slide once
opened and you have a gear up/down configuration difference that would prevent
the slide from blowing?  I know on the A320 the slide is operated secondary to
the door: after the off wing door is removed, the handle for the slide deploy
is exposed on the cutout frame.