DC9 question

[goaliemn]

I feel kinda dumb asking this, but I had a question on the DC-9. At the base of the tail section, there's a hole right above the body. What is that for?

 

[bocefus]

One hole is APU air inlet, other hole "the dirty one" is the APU exhaust

 

[LR25]

The oblong inlet at the base of the vertical stab is for ram air to enter the cabin if depressurised in flight, also for ground cooling if no packs are running.

 

[B767Inst]

I don't quite agree with LR25. The oblong hole is the ram air inlet for airflow across the ACM heat exchangers inflight. Inside the ram air ducting is a "ram air valve" which can be used to permit airflow during unpressurized flight. It is also used sometimes on the ground, with the right ground cooling fan, to circulate unconditioned air.

 

[pilotyip]

correct answer

and B767 is the winner, and for the next question, what is the purpose of the pitot tube above the hole in the vert stab.

 

[Singlecoil]

and B767 is the winner, and for the next question, what is the purpose of the pitot tube above the hole in the vert stab.

Doesn't that provide the airspeed input to the rudder travel limiting device, the porkchop?

 

[LR25]

I don't quite agree with LR25. The oblong hole is the ram air inlet for airflow across the ACM heat exchangers inflight. Inside the ram air ducting is a "ram air valve" which can be used to permit airflow during unpressurized flight. It is also used sometimes on the ground, with the right ground cooling fan, to circulate unconditioned air.

Isnt that what I said in a little less wording?

 

[Painkiller]

I believe that's the input for the rudder ratio module. Faster you go, less rudder input needed, slower you go, more rudder input needed.

I've changed a few of 'em.

 

[Jeff Helgeson]

Yes, it's the "Q-limiter" and moves the pork chop

More on the Ram air scoop. It is always heated with air foil anti-ice on via the both wing or tail......isn't that right FLX757!

 

[Painkiller]

I don't believe it's "always" heated. There is a button on the overhead labeled "tail". It either gets the flight attendant to the cockpit *tee hee*, or it cycles the anti ice valves to move the air from the wings to the tail.