AVSIG: Center Line Thrust wwswsigarch.jpg (7236 bytes)

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Ray Tackett
Top Gun


Reged: 04/30/04
Posts: 8892
Loc: Philadelphia, USA
Center Line Thrust
      #420866 - 01/18/16 11:54 AM

This is an offshoot of the CPL PTS discussion.

Obviously, a Cessna 337 is a multiengine aircraft with center line thrust.

What about multiengine aircraft whose thrust is close enough to the center
line that one would not expect a huge yaw moment on engine failure? I'm
thinking of DC-9/MD-80 and B727. Shorter fuselages, such as A-10 and
Citation might well have significant yaw with one engine out.

--------------------
Ray,

Owner, Lake Wood Be Gone

Turning quality lumber into sawdust and noise since 2013.


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sreyoB yrraL
AVSIG Member


Reged: 05/16/04
Posts: 9442
Re: Center Line Thrust [Re: Ray Tackett]
      #420868 - 01/18/16 12:07 PM

Quote:

What about multiengine aircraft whose thrust is close enough to the center
line that one would not expect a huge yaw moment on engine failure? I'm
thinking of DC-9/MD-80 and B727.



False premise.

A V1 cut in a DC9 takes full rudder, plus a little bit of aileron, to maintain heading as you climb at V2.

The DC8, with its four engines, required considerably less rudder when losing an outboard engine at V1. The V1 cut on the DC8 is a non-event in comparison.


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Dave Siciliano (ADS)
Top Gun


Reged: 05/17/04
Posts: 8469
Loc: ADS (Dallas, TX)
Re: Center Line Thrust [Re: Ray Tackett]
      #420874 - 01/18/16 02:59 PM

Larry would know those aircraft. For the Citation II and V I wouldn't say it's a non-even, but pretty manageable if above Vmc and more speed helps. V2 for us is always Vmc or more. Some of the AF folks had trouble with civil insurance with some of their fighters. The 337 of course, was centerline as was the Adam prototype that never came to fruition.

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Jeff Hartmann CIC
Top Gun


Reged: 05/18/04
Posts: 7323
Loc: Chico,CA
Re: Center Line Thrust [Re: Dave Siciliano (ADS)]
      #420879 - 01/18/16 03:41 PM

CJ-4 with 3600/side takes all the rudder.

--------------------
Jeff

nothing clever to say right now...


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Mase Taylor
Top Gun


Reged: 04/29/04
Posts: 9446
Loc: SOCAL
Re: Center Line Thrust [Re: Ray Tackett]
      #420880 - 01/18/16 03:58 PM

The F-4 Phantom is considered center-line thrust from the standpoint of a military pilot obtaining a civilian certificate.

--------------------
Fly The Airplane As Far Into The Crash As Possible. - Bob Hoover 1922-2016 R.I.P.


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sreyoB yrraL
AVSIG Member


Reged: 05/16/04
Posts: 9442
Re: Center Line Thrust [Re: Jeff Hartmann CIC]
      #420881 - 01/18/16 04:14 PM

Quote:

CJ-4 with 3600/side takes all the rudder.



Yep.

What people forget is that the designers give each airplane just as much rudder as it needs to meet the most restrictive certification criteria. For most twins that is the V1 cut. For the DC8 it was a two-engine-out (on the same side) go-around. The design must not only handle the situations where rudder is needed but it must handle situations where there is a rudder hard-over and the more authority the rudder has the more difficult that requirement will be to meet.


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Bill Bridges - 9S1
Top Gun


Reged: 05/17/04
Posts: 6008
Loc: 9S1
Re: Center Line Thrust [Re: sreyoB yrraL]
      #420882 - 01/18/16 04:32 PM

Quote:

there is a rudder hard-over and the more authority the rudder has the more difficult that requirement will be to meet.





For a rudder hard-over is differential power a viable option?

the other bill


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Ray Tackett
Top Gun


Reged: 04/30/04
Posts: 8892
Loc: Philadelphia, USA
Center Line Thrust [Re: sreyoB yrraL]
      #420886 - 01/18/16 04:59 PM

Thanks, yrraL. I asked seeking wisdom and found some.

--------------------
Ray,

Owner, Lake Wood Be Gone

Turning quality lumber into sawdust and noise since 2013.


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sreyoB yrraL
AVSIG Member


Reged: 05/16/04
Posts: 9442
Re: Center Line Thrust [Re: Bill Bridges - 9S1]
      #420887 - 01/18/16 05:07 PM

Quote:

For a rudder hard-over is differential power a viable option?



I do not know the certification requirements. I would not think that it would be based on using differential power for recovery.


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Gil Buettner [KAUW]
Top Gun


Reged: 05/16/04
Posts: 2847
Loc: Gateway to the Northwoods
Re: Center Line Thrust [Re: Ray Tackett]
      #420889 - 01/18/16 08:51 PM

My multi-engine rating was limited to centerline thrust after graduating from UPT with only T-37 and T-38 time.

When I returned to civilian life I took my C-130 records to the FSDO and had a new certificate without the restriction.

--------------------
-Gil


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