threefourthree
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First Thrust Reversers?

Tue May 27, 2008 5:15 am

Does anyone know when thrust reversers were first used and was it an option?
 
Pihero
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RE: First Thrust Reversers?

Tue May 27, 2008 9:13 am

Not a very well known story, ThreeFourThree.
There was once a genius called Jean Bertin...Unrecognised of course.
Among other inventions like the "Aerotrain", applications on hoovercraft like the "Terraplane", he designed the first *jet deviation device* in the early fifties while working for SNECMA.
The first application, on the "Goblin" turbojet of a DH "Vampire" was successfully fight-tested on 26 July 1952.

The first civilian application found it's way on the Boeing 707, a rather complicated ensemble of thrust reverser and noise suppressing pipes.
As far as I know, it was very early a feature of the airplane and was needed for certification, therefore not an option.
Another matter of interest is that the 727 engine position and reverser was tested on the "Dash 80".
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rwessel
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RE: First Thrust Reversers?

Wed May 28, 2008 3:49 am

Many of the big piston powered airliners had reverse pitch available for their propellers. Actually almost all aircraft with variable pitch propellers have a reverse position, since it's trivial to add at that point, and it's useful.
 
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HAWK21M
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RE: First Thrust Reversers?

Wed May 28, 2008 10:13 am

Was thinking just that.Reverse pitch propellers on the Piston Engined types should be the 1st of the T/Rs.

regds
MEL
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Pihero
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RE: First Thrust Reversers?

Wed May 28, 2008 12:14 pm

Sorry, guys,
Semantics are not my forte.
The way I saw the question, the subject is about jet engines.
The reverse pitch option has never been called a thrust reverser in my dictionary.The propeller effect is more a *pull* than a *thrust*.
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lapa_saab340
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RE: First Thrust Reversers?

Wed May 28, 2008 3:21 pm



Quoting Pihero (Reply 1):
The first civilian application found it's way on the Boeing 707, a rather complicated ensemble of thrust reverser and noise suppressing pipes.

I think they were used on the DH Comet first. Don't know if the original Comet 1 had them, but the RR Avon-powered versions had reversers on 2 of the engines.

Quoting Rwessel (Reply 2):
Many of the big piston powered airliners had reverse pitch available for their propellers. Actually almost all aircraft with variable pitch propellers have a reverse position, since it's trivial to add at that point, and it's useful.

Some of the airliners powered by radial engines did have reverse pitch, but aside from those reverse pitch tends to be the exception rather than the rule with most piston engine aircraft. Also many early turboprop aircraft did not have reverse pitch.
 
AirframeAS
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RE: First Thrust Reversers?

Fri May 30, 2008 8:32 pm



Quoting Rwessel (Reply 2):
...reverse pitch...

Isn't that the same as feathering the prop?
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KELPkid
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RE: First Thrust Reversers?

Fri May 30, 2008 8:40 pm



Quoting AirframeAS (Reply 6):


Isn't that the same as feathering the prop?

Negative. Feathering the prop is turning the blades so that they are 90 degrees to the slipstream, and is done to reduce drag when you loose a mill in a mult-engined bird. Reversing pitch is turning the blades so that the propeller is producing thrust in the opposite direction to the usual direction.

If you think of the propeller blades as spinning airfoils (which they are), then you see how this makes sense  Smile
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HAWK21M
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RE: First Thrust Reversers?

Sat May 31, 2008 9:29 am



Quoting KELPkid (Reply 7):
Negative. Feathering the prop is turning the blades so that they are 90 degrees to the slipstream, and is done to reduce drag when you loose a mill in a mult-engined bird. Reversing pitch is turning the blades so that the propeller is producing thrust in the opposite direction to the usual direction.

Thats correct.Feathering produces "almost" no thrust.
regds
MEL
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Asturias
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RE: First Thrust Reversers?

Sat May 31, 2008 4:42 pm

I can't agree that props produce thrust. Jets produce thrust, their power measured in N, props produce work measured in W.

Quoting Pihero (Reply 4):
The reverse pitch option has never been called a thrust reverser in my dictionary.The propeller effect is more a *pull* than a *thrust*.

This I agree with.

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AirframeAS
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RE: First Thrust Reversers?

Sat May 31, 2008 5:57 pm



Quoting KELPkid (Reply 7):
Feathering the prop is turning the blades so that they are 90 degrees to the slipstream,

Which I already know that. They taught us that in A&P program in the Propellers class. Just wanted to double check. I don't deal with Propellers.
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Santhosh
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RE: First Thrust Reversers?

Tue Jun 03, 2008 7:36 am

While dealing with a one engine out situation in a twin engine aircraft. Do pilots deploy the reverser on the other running engine upon landing or just simply brake since the activation of the reverser would cause the moment arm which would tend the aircraft to deviate off the course?

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George
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DashTrash
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RE: First Thrust Reversers?

Tue Jun 03, 2008 4:42 pm



Quoting Santhosh (Reply 11):
While dealing with a one engine out situation in a twin engine aircraft. Do pilots deploy the reverser on the other running engine upon landing or just simply brake since the activation of the reverser would cause the moment arm which would tend the aircraft to deviate off the course?

Depends on the airplane.
 
SlamClick
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RE: First Thrust Reversers?

Tue Jun 03, 2008 5:27 pm



Quoting Asturias (Reply 9):
their power measured in N

Actually "N" in jet engines is the measurement of the rotational speed of the engine rotors, usually expressed as a percentage of their total rated RPM. The thrust represented by the N1 value is calculated, not measured.

True EPR, the actual comparison of PT1 and PT7 comes closer to actual measurement of thrust but still requires the charts to know the relative area of intake and exhaust.

Quoting Asturias (Reply 9):
I can't agree that props produce thrust.

Well, in discussions of the "four forces" in flight, they do produce the one opposite "drag" so if you have a better name for that perhaps we could change convention. One might find fault with any of the usual expressions but they have the virtue of being comprehensible to student and professional alike.
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Pihero
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RE: First Thrust Reversers?

Tue Jun 03, 2008 5:43 pm



Quoting SlamClick (Reply 13):
they do produce the one opposite "drag" so if you have a better name for that perhaps we could change convention.

I am for *pull* or *traction*, both physically and thermodynamically correct, aren't they ?
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SlamClick
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RE: First Thrust Reversers?

Tue Jun 03, 2008 6:13 pm

Personally I think they move by propelling air rearward. The air, in turn pushes the surface of the earth in that direction. As a side effect they cool the pilot.

An Army instructor argued that the propeller on the L-19 (or O-1) Bird Dog was a pusher as it pushed against the underside of the bolt heads attaching it to the crankshaft flange. I countered that it pulled equally against the underside of the nut behind that flange. We never did resolve that.
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2H4
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RE: First Thrust Reversers?

Tue Jun 03, 2008 6:41 pm



Quoting SlamClick (Reply 15):
An Army instructor argued that the propeller on the L-19 (or O-1) Bird Dog was a pusher as it pushed against the underside of the bolt heads attaching it to the crankshaft flange. I countered that it pulled equally against the underside of the nut behind that flange. We never did resolve that.

I wonder if, through the entirety of aviation, anyone has ever mounted a propeller on each end of a single crankshaft. This would result in a pusher and puller configuration.

2H4
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SlamClick
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RE: First Thrust Reversers?

Tue Jun 03, 2008 6:44 pm



Quoting 2H4 (Reply 16):
anyone has ever mounted a propeller on each end of a single crankshaft.

Of course you are well aware of historical examples of tractor and pusher propellers installed on the same nacelle but driven by two engines.

Single crankshaft? Where would the pilot sit?
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2H4
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RE: First Thrust Reversers?

Tue Jun 03, 2008 6:46 pm



Quoting SlamClick (Reply 17):
Single crankshaft? Where would the pilot sit?

Same place. The engines would be out on the wings.  Wink

2H4
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Pihero
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RE: First Thrust Reversers?

Tue Jun 03, 2008 6:56 pm



Quoting SlamClick (Reply 15):
The air, in turn pushes the surface of the earth in that direction. As a side effect they cool the pilot.



Quoting SlamClick (Reply 15):
I countered that it pulled equally against the underside of the nut behind that flange. We never did resolve that.

This is getting too hot for me.

I need a fan !




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Jetlagged
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RE: First Thrust Reversers?

Tue Jun 03, 2008 8:57 pm



Quoting SlamClick (Reply 13):
Quoting Asturias (Reply 9):
their power measured in N

Actually "N" in jet engines is the measurement of the rotational speed of the engine rotors

Suspect Asturias means Newtons, but more usually it would be in kN, or of course old fashioned lbs.

Quoting Asturias (Reply 9):
props produce work measured in W.

Propeller engine output is shaft power, measured in shp or kW. Work is not.

However a propeller itself certainly does produce thrust. It is what pushes (or pulls) the aircraft along.

Quoting Pihero (Reply 14):
I am for *pull* or *traction*, both physically and thermodynamically correct, aren't they ?

Certainly not traction, which requires friction to work. "Pull" maybe, but I would have thought a pilot would much prefer a bit of "thrust".  Wink
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Pihero
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RE: First Thrust Reversers?

Tue Jun 03, 2008 9:20 pm

Not you too !!!!!  Wink


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bond007
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RE: First Thrust Reversers?

Wed Jun 04, 2008 1:01 am



Quoting Jetlagged (Reply 20):
Certainly not traction, which requires friction to work.

You mean friction .. like friction against the air?

Isn't that why the prop displaces the air ... and doesn't displace as much 'thin' air  Wink

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Jetlagged
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RE: First Thrust Reversers?

Wed Jun 04, 2008 11:34 pm



Quoting Bond007 (Reply 22):
You mean friction .. like friction against the air?

Isn't that why the prop displaces the air ... and doesn't displace as much 'thin' air

A prop would still work without friction. It creates lift in the forward direction, which becomes thrust.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
SlamClick
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RE: First Thrust Reversers?

Wed Jun 04, 2008 11:42 pm



Quoting Bond007 (Reply 22):
.. like friction against the air?

Or a conveyor belt.
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Starlionblue
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RE: First Thrust Reversers?

Thu Jun 05, 2008 12:12 am



Quoting SlamClick (Reply 24):
Or a conveyor belt.

Slay him.
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bond007
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RE: First Thrust Reversers?

Thu Jun 05, 2008 12:38 am



Quoting Jetlagged (Reply 23):
It creates lift in the forward direction, which becomes thrust.

... and that lift is directly proportional to the air density  Wink

Quoting SlamClick (Reply 24):
Or a conveyor belt.

...only if the speed of the propellor matches the speed of the belt ....


Jimbo
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2H4
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RE: First Thrust Reversers?

Thu Jun 05, 2008 12:52 am



Quoting Bond007 (Reply 26):
and that lift is directly proportional to the air density

Not to mention the number of hovering birds in the cabin.

2H4
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WPIAeroGuy
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RE: First Thrust Reversers?

Thu Jun 05, 2008 1:01 am

What if the propellor and plane stays stationary and the air spins around the fuselage?
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bond007
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RE: First Thrust Reversers?

Thu Jun 05, 2008 1:35 am



Quoting WPIAeroGuy (Reply 28):
What if the propellor and plane stays stationary and the air spins around the fuselage?

Well, it's much more interesting for the passengers (and crew!), if the propellor stays stationary and the plane spins.

I think that starts to happen when you make the propellor bigger and bigger.

Jimbo
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Jetlagged
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RE: First Thrust Reversers?

Thu Jun 05, 2008 2:19 am



Quoting Bond007 (Reply 26):
... and that lift is directly proportional to the air density

Amongst other things of course.  Smile
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osiris30
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RE: First Thrust Reversers?

Thu Jun 05, 2008 5:19 am



Quoting SlamClick (Reply 24):
Or a conveyor belt.



Quoting Starlionblue (Reply 25):
Slay him.

BWHAHAHAHAHHA.. well played  Smile

Quoting Bond007 (Reply 26):
...only if the speed of the propellor matches the speed of the belt ....

And another one  Smile

Great thread guys, thanks for making me smile  Smile
I don't care what you think of my opinion. It's my opinion, so have a nice day :)

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