Aircraft Engineering Question

[Ahmet H]

Just a quick question,

A friend of mine today was talking about how aircraft engineers attach an extra engine to a planes wing to cart it to another location rather than putting it in cargo or on a cargo plane. For example with on a 747 they add a third engine on the wing as close as they can to the fuselage.

He also said that they can do this while passengers are on board the flight, and that they can attach it to only 1 wing. So for example a 747 having in total 5 engines attached to it.

Is he pulling my leg or is any of this true?

Now he has provided evidence with a photo, but Photoshop does many lovely things these days.

Thanks for the help.

[Nigel C]

Very true. It's called '5th pod' operations.

[Daniel F]

Here's some more evidence...
http://www.airliners.net/photo/Qanta...438/0289429/M/

[Sarah C]

There are quite a few pics on airliners.net, mainly of the QF 747's (Rolls Royce engines) operating the 5th pod. One of the moderators, Will Tidmarsh, has operated a couple of these 5th pod flights.

[Adrian B]

I am sure the guys aka Wil will (?) fill you in, but there are obvious penalties attached when running these ops, ie fuel, MTOW and range. Those in the know will correct me or provide the info in question??

[Philip Argy]

What does the 5th pod weigh? Are the left and right fuel tank loads adjusted to compensate or is the turning moment neglible when it hugs the fuselage so closely?

[Brenden S]

There is a code entered into the computer which offsets the conditions. Will has actually posted a very informative post when he did the last v-pod operation. It also comes up on the pilots screen saying V-Pod or something along the lines of such. There is severe penalty restrictions imposed on the aircraft but its all approved. On the jumbo there are attach points for the V-Pod pylon to be bolted up. You can put any RR engine onto the pylon as the bolts all match up. The aircraft that can carry a spare engine are B747-100,-200,-300,-400, B707, L1011 and a Tristar I think. Engines for the jumbo are the P&W JT9 and RR all variants.

B744 carrying a B743 Engine
http://www.jetphotos.net/viewphoto.php?id=329043
B743
http://www.jetphotos.net/viewphoto.php?id=311622
http://www.jetphotos.net/viewphoto.php?id=311625

[Bernie P]

Originally Posted by Brenden S

There is a code entered into the computer which offsets the conditions. Will has actually posted a very informative post when he did the last v-pod operation. It also comes up on the pilots screen saying V-Pod or something along the lines of such. There is severe penalty restrictions imposed on the aircraft but its all approved. On the jumbo there are attach points for the V-Pod pylon to be bolted up. You can put any RR engine onto the pylon as the bolts all match up. The aircraft that can carry a spare engine are B747-100,-200,-300,-400, B707, L1011 and a Tristar I think. Engines for the jumbo are the P&W JT9 and RR all variants.

B744 carrying a B743 Engine
http://www.jetphotos.net/viewphoto.php?id=329043
B743
http://www.jetphotos.net/viewphoto.php?id=311622
http://www.jetphotos.net/viewphoto.php?id=311625

Is it only on the LEFT wing that can carry these, or can both sides??? And, is the location for it under panels as well, and therefore not that noticable whn not installed?

[Ahmet H]

Well thanks guys for all that info! I had no idea it could be done. What are the benifits? Wouldn't it be easier to put it in cargo?

[Craig Murray]

Originally Posted by Ahmet H

What are the benifits?

Engine is carried externally and doesn't require a cargo aircraft to be sourced to transport the engine to the destination when logically the airline with the stranded aircraft will have regular services to that port.

Originally Posted by Ahmet H

Wouldn't it be easier to put it in cargo?

If it would fit, possibly. But it would come at the cost of revenue freight and would thus cost the airline money. Given they already have an aircraft on the ground earning no money the airline will be trying to minimise any losses. Being able to carry a 5th engine makes doing this just that little bit easier.