Advantages of Pod engines

[erniefly]

Can anyone detail the advantages of Pod engines compared to having the engines mounted on the back of the aircraft.

Thanks for any help.

[Ka8 Flyer]

Well I can think of three at the moment:

a) Not as noisy as fuselage mounted engines.

b) More space! Would be pretty interesting to see the engines of the 777-300ER mounted on the fuselage ;)

c) If more than 2 engines are mounted side-by-side on the fuselage (ie 4 engines in total), a fire could spread more easily than on the wing.

Disadvante would be the yaw effect if an engine failed on one side.

Regards,

Mark

[John Farley]

Some advantages, of which the first one probably tops any list:

The weight of the engines reduces the wing tip up bending effects of lift allowing a lighter wing structure.

It may be a little easier to arrange for a suitable structural fuse that allows the engine to break free from a wing pylon under engine seizure or other severe event.

Routine maintenance access can be easier as the engines are likely to be closer to the ground.

Although engines are normally certificated on the basis that they will contain any blades they shed, this does not always happen in practice. Moving the engines out on the wing can help following such an event. Certainly the closer engines are together the easier it is for a bad structural event in one to damage another.

The whole business of choosing an overall aircraft configuration is a compromise of many issues.

[Genghis the Engineer]

Also it makes life much easier for the designer to change what engine is fitted, since by and large only the pod needs a redesign, not large chunks of primary aircraft structure. Can you imagine the task of installing a bigger engine in a DH Comet.

And it saves a complete re-think on CG positioning if a sunstantially heavier (or lighter) engine is fitted later, podded engines are pretty close to the CG operating range, tailmounted engines are not.

G

[twistedenginestarter]

To clarify what John Farley is saying, putting the engine on the wing spreads weight away from the fuselage which allows the wing to be less rigid, On the wing they can be stuffed out in front to provide a bending moment about the wing axis which again means you can make the wing less strong.

Probably the only reasons planes don't have them on the wing are:

1) you need a taller/heavier landing gear

2) you need a bigger tail to compensate for engine failure at low speed.

[BigGreenPleasureMachine]

A few other benefits include fuel delivery to the engine: easier when its hung under the fuel tanks in the wing/centrebox and there can also be advantages from the pylons acting as wing fences, allowing aerodynamicists to do even less work;-)

[Joe Bolt]

The VC-10 (4 aft fuselage mounted RR Conways) has specially shaped main-gear tyres, which prevent water from the runway being thrown up and ingested by the engines. This isn't an issue with pod mounted engines.

[compressor stall]

Disadvantage is FOD ingestion

[dogcharlietree]

Hate to disagree Mark;
a) Not as noisy as fuselage mounted engines.
I think it was a LOT quieter in the front of the cabin of a Diesel 9 or 727 compared to a 767, A300, 737 etc.
Just my thoughts :-)

[Ka8 Flyer]

Hi DCT,

I have to admit, I only have MD80 "experience", haven't been on a 727 for a very long time.
What I mean is that sitting in the rear in a MD80 is much louder than sitting "on the wing" of a 737/767 etc.

Regards,

Mark

[Tinstaafl]

Some relevant stuff at this thread: http://www.pprune.org/forums/showthread.php?s=&threadid=106985&highlight=pod+mounted+engines

[Specnut727]

I have read that Boeing pioneered the use of pod mounted engines to meet a US Military requirement, that a catastrophic engine failure should not jeopardise any major structural components.

Also, when Boeing engineers first saw details of the Comet, they were rather 'amused' by the engine location !!

[noisy]

Specnut,

I suspect that DH were trying to make the best of not-very-powerful engines by having the cleanest aerodynamic configuration that they could manage.

[Noise Unit]

Genghis wrote

'Can you imagine the task of installing a bigger engine in a DH Comet.'

You do not need to imagine it, it's almost real and called putting the BR715 into the Nimrod....:O

[cirrus01]

Advantages of Pod engines ..........so you can go Pod racing with them ....of course !!!


(Star Wars eps 1):ok: :ok: :ok:

[Mad (Flt) Scientist]

In addition to the structural wing bending relief mentioned above, pod mounted engines, when suspended far forward of the wing, can provide a substantial additional amount of aeroelastic relief.

[GearDown&Locked]

Out of simple observation, wouldn't it be a major point against POD mounted engines, if the a/c finds itself in a landing gear faillure situation, and has to make a belly-landing?:ouch:

[cirrus01]

Geardown&locked.......(or not as in this case := )

Underslung pod engines will usually depart from the airframe due to forces which will shear the "fuse pins" . Part of the design for just this event.

:ok: