Low RPM's during run up/take off

[wldlndfirefghtr]

Richard,

Really appreciate the data. Makes me a bit less concerned, but still need to get back up and fly 26D and see where she sits. Everything is pointing to normal, just lower compressions due to sitting. When I get back up I'll post some numbers as well.

Thank you again.

Jason

[wldlndfirefghtr]

All,

Went up today, again right at gross, DA about -1900. Takeoff rpm 2100, slowly climbing on take off roll, around 1000' just hitting 40mph. Aborted takeoff followed by 2 high speed taxis.

Well I suppose next step is to pull the prop and check the pitch. Suggestion was to also see if the brakes were dragging. CFI believes it to be an engine performance issue, not producing power/not feeling the acceleration. I'm at a loss. Here was what was done previous to this flight;

(O300D) Performed compression test (68, 62, 72, 63, 67, 63) re-timed both magnetos to 28 degrees BTDC. Cleaned , re-gapped plugs, cleaned treated for corrosion, performed bore scope inspection on exhaust system for obstructions- none found, ops checked carb heat box and carb throat for obstructions and defects- none found. Inspected throttle, mixture, carb heat control travel limits and stops, performed static run up, satisfactory.

Mechanic believes prop to be a cruise, based on eyeballing it, no note of re-pitching in prop logbook.

Thinking of getting 2nd opinion....

Suggestions......

Thanks again.

[n2582d]

re-timed both magnetos to 28 degrees BTDC. ... Suggestions...

The right magneto should be timed to 26 degrees.

[Bruce Fenstermacher]

Jason, I reread this entire post. How long have you had this plane? In other words do you know the plane to have produced more RPM with this prop?

If the answer is yes it made more RPM under the same circumstances then either it is a recording error or something not quite right.

Both mags timed at 28° is not quite right.

A leaking carb heat valve is not quite right. Disconnect scat duct from carb box to see if it makes a difference on a test run high speed taxi.

Running rich is not quite right. Lean for best RPM on the ground and see if that makes a difference. If it does then I'd be looking at the carb venturi or just the over all condition of the carb. Your primer, if leaking can also be a source or a rich running engine. It could be disconnected for testing purpose and eliminating it from the trouble shooting process.

If static RPM is OK but you don't develop RPM on the roll and your ground roll is extended, I'd look at dragging brakes, tire inflation and even pilot technique.

It would also be nice to know what pitch prop your trying to turn. This info could explain a lot.

[c170b53]

With the last few posts (engine ticking sound) it's tough to discern what's going on when info is missing. What may be obvious to the owner may end up as white space for those reading and trying to understand the real issue. It doesn't really matter in the long run as just about everything can be solved given sufficient time and money. For me, I think of the situation first and then the symptom as reported. So maybe I'm wrong often and I guess a lot The first thing I think about with this problem; Alaska this time of year, cold thick air and I would think any airplane even a original engined Swift would jump into the air if the engine was producing it's rated power. Hopefully more info will help us understand further the issue.

[blueldr]

That mechanic must be a real whiz bang if he can eyeball a prop and guess the difference between a 53 and 55 inch pitch. Is he the one who timed both mags at 28 deg. BTC?

[Bruce Fenstermacher]

With the last few posts (engine ticking sound)

Engine ticking? Jim that was another thread. Keep up with us won't ya onced now.