Engine Bog Down

[Arfur Feck-Sake]

Can anyone explain engine "bog down" in simple terms for me?

Thanks in advance.

[lomapaseo]

Can you describe the symptoms?

I've never heard of the term used in a manual of operation.

[pjvr99]

Common on RR Allison T56/501. During starting engine will not accelerate to low speed ground idle (72%) after starter button release, or will not accelerate to normal ground idle. Has a tendency to surge/stall once started. Normally caused by dirty fuel nozzles, dirty compressor and/or turbine, or fuel control unit has shifted to lean.

[13 Mile Arc]

What pjvr99 has described is a stalled or stagnated start , Bog Down , occurs most often in the T56 when pwr demanded is greater than power available , such a selecteing reverse at high speeds with a high OAT , the RPM will decay outside normal limits and the engine will wind down , if the power lever is advanced to reduce blade angle RPM should recover .I have a LM brochure produced for a C130 operators conference and they use the term "Unscheduled rundown" to describe "bog down".

[barit1]

Other OEMs & operators have used the term "cold hangup" to describe similar symptoms (no accel, low ITT/TIT/EGT).

[pjvr99]

13 Mile Arc - What pjvr99 has described is a stalled or stagnated start , Bog Down , occurs most often in the T56 when pwr demanded is greater than power available , such a selecteing reverse at high speeds with a high OAT , the RPM will decay outside normal limits and the engine will wind down , if the power lever is advanced to reduce blade angle RPM should recover .I have a LM brochure produced for a C130 operators conference and they use the term "Unscheduled rundown" to describe "bog down".

:ugh: 13MA is correct (sorry, early morning). Sometimes it's difficult to determine whether bogdown, stagnation or flameout occurred, depending on the crew reports. However, the same checklist is used to verify/rectify these 3 conditions.