F-80, T-33 QUESTION

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Joe Gopan
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F-80, T-33 QUESTION

Post by Joe Gopan » Thu Dec 27, 2018 4:01 am

Saw my first F-80 overhead around 1947-48 and have always wondered, but forgot to ask, what causes the "moaning noise" they make during a slow pass in preparation for landing. It's similar to blowing into a Coke bottle sound. Would it have something to do with the two spring loaded doors just behind the cockpit?
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Wolfman
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Re: F-80, T-33 QUESTION

Post by Wolfman » Thu Dec 27, 2018 6:50 am

Seems I have heard this discussion. As I recall, the F-80 was a single engine aircraft but had two fairly large intake nacelles on each side of the fuselage. When the engine was up to speed, air was drawn in through the nacelles but when the engine idled back, for landing, as in your question, there was more air than the engine would accept, so the excess air was blown out around the intake nacelles and produced the " moaning sound". Like blowing over a pop bottle.
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Joe Gopan
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Re: F-80, T-33 QUESTION

Post by Joe Gopan » Thu Dec 27, 2018 6:57 am

There are air ducts at the opening of the intakes that have something to do ewith boundry air,and there are those two spring loaded doors about 3' X 1'behind the canopy. I'll try a web search.
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Wolfman
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Re: F-80, T-33 QUESTION

Post by Wolfman » Thu Dec 27, 2018 7:01 am

So what you are saying is, when the engine idled down, the spring loaded doors opened on their own to dump the excess air being rammed into the intake nacelles ??
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Re: F-80, T-33 QUESTION

Post by Joe Gopan » Thu Dec 27, 2018 7:16 am

No idea really, but I always seemed to witness the event upon slow approach to the airfield by this type aircraft, not sure if they were throttling up or down.
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Re: F-80, T-33 QUESTION

Post by GI. » Thu Dec 27, 2018 12:28 pm

The F-80 and the T-33 had the centrifugal flow eng. in them, the rest had the axial flow, the spring loaded doors behind the cockpit [called plenum chamber doors] were to allow more air to the eng. while on the ground, eng. run up and take off roll, once the acft. was in the air it got enough air thru. the two intake ducts and the spring loaded doors were no longer needed and closed.
The centrifugal and axial flow eng's were two comp. diff. eng,s, that might might be why they sounded diff. to you, they were also a less powerful eng. then the J-47 or the J-57 which were in the F-86 and the F-100.
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Re: F-80, T-33 QUESTION

Post by Wolfman » Fri Dec 28, 2018 6:44 am

Good intel, GI.
I searched for quite a while before finding a picture of the doors open. On top, right behind the canopy. Two doors, side by side, that hinged on the front and opened up and to the rear. In the picture, they looked to be hydraulically activated.
My first thought was speed brakes, but their size did not make sense. Too large to be sticking out in a 600 MPH slip stream. Second thought, that was a strange place for speed brakes.
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Re: F-80, T-33 QUESTION

Post by Joe Gopan » Fri Dec 28, 2018 9:53 am

Spring loaded, you can push them inward by hand.
I can remember a T-33 Crew Chief explaining that the air pressure around the engine on the T-33 was something like 4 atmospheres, and I may stand corrected on this.

I had a brainstorm and did a search on F-80 Jet Engine Chamber Doors and that they allow extra air for the jet engine at speeds below 200 knots. Maybe that is the source of the noise in question as I only witnessed it on F-80's and T-33's in the immediate vicinity of the air field.
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Re: F-80, T-33 QUESTION

Post by GI. » Fri Dec 28, 2018 1:13 pm

The T-33 and the F-80 both had the Allison J-33 engine, take off speed was around 105 to 115 knots, landing speed around 90-95 knots. they both did have speed brake's [speed boards] on the bottom of the acft. they also could carry a small baggage pod on their belly.
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Re: F-80, T-33 QUESTION

Post by Joe Gopan » Fri Dec 28, 2018 2:07 pm

Look Familiar? :wink: Speed Boards are up in the photo.
F-80, F-84, F-86 sights like this were familiar constantly thru the mid 50's at Dow Field
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2011 MVPA PIONEER AWARD - MVPA #1064
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Joe Gopan
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Re: F-80, T-33 QUESTION

Post by Joe Gopan » Fri Mar 05, 2021 7:39 am

Looking for one more 1/5 scale F-80 or T-33.
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