CalAir
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Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 9:58 am

If you look at the photo below, the 747-100 has holes on the engine cowlings, that other early 747 photos I have seen do not, what is their purpose?


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Photo © Shary(Shahram)

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SFOMB67
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 12:15 pm

Don't know the technical name for them, but they're spring loaded doors that open under eng acceleration to allow more air into the engine. What that thing behind the APU ? Test equip ?
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474218
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 12:39 pm

Quoting Sfomb67 (Reply 1):
What that thing behind the APU ? Test equip ?

In-flight refueling boom (flying boom).
 
speedracer1407
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 1:00 pm

I believe those little doors (whatever they're called) were on the original JT9-D 747 engines, but were later considered unnecessary following a redesign of the intakes.
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LTU932
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 5:09 pm

Quoting Speedracer1407 (Reply 3):
I believe those little doors (whatever they're called) were on the original JT9-D 747 engines, but were later considered unnecessary following a redesign of the intakes.

Those small inlets were also present on the 707 with JT3D turbofans. Those with pure jets and with the Rolls Royce Conway turbofan don't seem to have those smaller inlets.
 
VC-10
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 7:43 pm

Quoting Sfomb67 (Reply 1):
Don't know the technical name for them

Secondary Inlet Doors
 
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HAWK21M
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 8:23 pm

JT9Ds with Blow in Inlet doors/Secondary Inlet Doors.
What would be the Tanker capacity.

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MEL
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TropicBird
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RE: Holes On The Cowlings Of The 747?

Sun Apr 16, 2006 11:42 pm

We used to call them "blow in doors".
 
dw747400
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 1:11 am

Are they mechnaically actuated or does the airflow force them open under certain circumstances?
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HAWK21M
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 1:55 am


Quoting Dw747400 (Reply 8):
Are they mechnaically actuated or does the airflow force them open under certain circumstances

The ones on the JT8D powered B737s operate mechanically by Airflow thru them at low RPM.
Presume it would be the same on these too.
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MEL

[Edited 2006-04-16 18:59:52]
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VC-10
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 2:16 am

Quoting HAWK21M (Reply 9):
The ones on the JT8D powered B737s operate mechanically by Airflow thru them at low RPM.

They are spring loaded closed & open by suction at HIGH RPM
 
CalAir
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 2:20 am

Cheers guys, wondered why I hadn't seen them before!
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HAWK21M
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 2:29 am

Quoting VC-10 (Reply 10):
They are spring loaded closed & open by suction at HIGH RPM

True they are Spring loaded.Wouldn't High RPM/Thrust provide adequate thrust thru the Inlet Duct,not requiring the opening of the blow in doors.
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MEL
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VC-10
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 2:47 am

They open at high RPM - low forward airspeed.

When I was involved in 707 Eng Runs they woul be 'cracked' open at idle & fully open by 'part power'
 
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HAWK21M
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RE: Holes On The Cowlings Of The 747?

Mon Apr 17, 2006 2:58 am

Quoting VC-10 (Reply 13):
They open at high RPM - low forward airspeed

Thats correct.
regds
MEL
I may not win often, but I damn well never lose!!! ;)

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