Drag of a Seized Turbofan

[JABBARA]

Hi,

A question, keep searching in the web but no clear answer yet.

A failed Turbofan engine, with a Fan (N1, Low Pressure Compressor/Turbine) which is either totally seized or nearly seized:
What is its drag as compared to a simply failed engine with no damage?
And why?

Thanks in advance

[decurion]

The effect of taking shaft power from a windmilling engine is to decrease rotational speed and airflow. The airflow reaches a minimum at locked-rotor conditions. Internal drag will therefore change (see references below).

The spillage drag is also likely to increase due to the reduction in airflow through the engine. Spillage drag will be a maximum at locked-rotor conditions.

See also http://aerade.cranfield.ac.uk/ara/1952/naca-rm-e51k15.pdf

and

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930094390_1993094390.pdf

[JABBARA]

Decurion,

That`s good answer,

Thanks again

[JABBARA]

Decurion
After I reviewed the documents I am a little bir confused with your comment:

The spillage drag is also likely to increase due to the reduction in airflow through the engine.

With the term "Spillage Drag" I understand the drag formed as forcing some intake air around the engine rather than through the engine due to locked fan. That makes sense, this makes an increasing drag however -what I understand from first document`s initial paragraphs- the "internal drag" not increase, on the contrary decreases with a locked engine. At the end, there is no clue that in which direction (decrease or increase) the whole drag (total drag) of the engine changes.

Do I miss something?

If you can kindly explain.

Thanks

[decurion]

The breakdown of the forces associated with a propulsion system into “thrust” and “drag” is to some extent arbitrary. It can indeed be confusing sometimes and good booking is important in the end.

Spillage drag is related to flow conditions above and below the mass flow ratio at which flow separation occurs at or near the cowl lip. This can be infleunced by the locked-rotor condition.

There should be many NACA/NASA studies on this topic giving more background.

[Tinribs]

I spent about fifteen years flying the 737 3/4/5 and never found the simulater to err in any performance respect

Even details, if an engine fell off the zero fuel weight went down by the appropriate amount

The sim aircraft performance suffered markedly with an engine failed with fan siezed at V1 but it was still within the climbout spec if the approved technique and speeds were followed but not if higher speeds were used