# Does Raymer's installed engine equation include the weight of the pylon?

I am currently modelling an aero engine and require the weight breakdown of the individual components, I have the dry weight of the engine and need to verify the pylon and nacelle weight.

Raymer has presented an equation for the weight of the installed engine in his book $$W_{InstalledEngine} = 2.575 *(W_{Engine})^{0.922}*N_{engine}$$

Does this include the pylon?

• The equation is probably a (nonexact) curve fit to some data. So you have some variation around the equation to start off with. The error from the pylon (either way) weight could be insignificant, so you might as well ignore it. Just my opinion. Nov 30, 2018 at 10:37
• Nengine is the number of engines on the aircraft. Nov 30, 2018 at 10:43

No, it doesn't include the pylon. If you think about it, the engine is installed on the pylon, which is part of the aircraft's fuselage or wing structure and not part of the engine.

You can see what I mean by watching this video of the replacement of an engine on an American Airlines 777.

Raymer's equation does include the nacelle and other auxiliary equipment installed on the engine.

I do not have access to Raymer's book, only to Torenbeek. Section 8.4.2 states:

Thus a specification of the definitive engine weight $$W_e$$ is usually available comprising:

1. engine weight, bare and dry,
2. standard engine accessories and
3. additional weight contributions such as gas generator cowling and/or noise suppression material.

Since the pylon is not listed there, we can safely assume that pylon weight is not included in $$W_e$$