Plane seems to have lost some of its power

SixPapaCharlie

SixPapaCharlie

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We have had our plane for a year and a half.
We are perceiving that it has less power than when we initially got it.

Last summer we had 2 full grown adults in it (me @ around 190 lbs) and the other two about 220-240.

Never seemed to have much issue getting up.

Seems lately dad and I keep having conversations about climbing out and playing with a really small sweet spot in the pitch. Stall horn seems to be going off more easily climbing out.

The RPMs are okay and the only thing I can think of is maybe having had the prop sanded down a few times. Does that have a major impact on power? It would make sense to me that smaller prop at same RPM yields less power.

We used to be on gravel and had it sanded down 3-4 times to get nicks out.

Compressions were good at the annual in May but Dad and his friend flew today and used up too much of a 3000 foot runway getting it to Vy.
It just seems like it is getting weaker.

I am doing two flights tomorrow. Anything specific you think I should pay attention to?
 
How are the temperatures this summer compared to last? Have your flying habits changed any? Has your cruise speed changed any?
 
SixPapaCharlie said:
We have had our plane for a year and a half.
We are perceiving that it has less power than when we initially got it.

Last summer we had 2 full grown adults in it (me @ around 190 lbs) and the other two about 220-240.

Never seemed to have much issue getting up.

Seems lately dad and I keep having conversations about climbing out and playing with a really small sweet spot in the pitch. Stall horn seems to be going off more easily climbing out.

The RPMs are okay and the only thing I can think of is maybe having had the prop sanded down a few times. Does that have a major impact on power? It would make sense to me that smaller prop at same RPM yields less power.

We used to be on gravel and had it sanded down 3-4 times to get nicks out.

Compressions were good at the annual in May but Dad and his friend flew today and used up too much of a 3000 foot runway getting it to Vy.
It just seems like it is getting weaker.

I am doing two flights tomorrow. Anything specific you think I should pay attention to?
Click to expand...

What engine instrumentation do you have? Tach & MP gauge? What do they show and how do the readings compare to previous readings?

What airplane/engine? You could be suffering from cam wear if you're flying behind a Lycoming.
 
Ted DuPuis said:
How are the temperatures this summer compared to last? Have your flying habits changed any? Has your cruise speed changed any?
Click to expand...

Today was cool (mid-high 80s).

Cruise speed is ok

Engine is Lycoming 320


Habits haven't changed much except we were both essentially new pilots last year and now we have each added a couple hundred hours to our logbooks.

Actually one major change now that you mention it...
Last year we were at an airport w/ a 3200 ft runway. We have since relocated to an airport with a 7000 ft runway. It could be a perception thing when taking off from those 3k strips now that we have been at the longer strips

Only thing is Neither he or I were ever concerned last year that we were under powered or eating up too much runway.
 
Only engine instrument is tach.
Fixed pitch, no EGT/CHT or anything of that nature.
 
Do you know how your compressions are running now compared to last year? Might have a leaky valve. I had a C150 years ago that developed a sticking valve and the first thing i noticed was reduced power.
 
MickYoumans said:
Do you know how your compressions are running now compared to last year? Might have a leaky valve. I had a C150 years ago that developed a sticking valve and the first thing i noticed was reduced power.
Click to expand...

We are going to get them checked next week.
Would that cause a drop in power at the same RPM?
 
A worn camshaft is the prime culprit in gradual loss of power when the compressions and all other indications are normal.
 
SixPapaCharlie said:
... Stall horn seems to be going off more easily climbing out.
Click to expand...

Ummm... What speed are you climbing out at?

http://www.1worldaero.com/aircraft/tb9-tampico/

Click on the Checklists link. Rotate at 65 kts, climb out at 75 kts.

You should not be getting a stall warning horn at 75 kts.

I kept falling back on my Cessna 172 numbers and trying to climb out at 65 kts. Once I broke that habit it got better results.

The same is true for your best glide speed. It's 86 for out Tampicos! If you slow down to 65 it drops like a rock!

Jim
 
If there's actually a loss of power, then I'd agree the camshaft is a likely culprit.

It can be difficult to get data that truly seems to indicate how a plane is performing. I think cruise speed is often the best measure of this, but probably not so much on a fixed pitch prop where you just advance the throttle more to get the same RPM. You don't see the difference in MP.

If you truly suspect that there's a power loss, look at the cam. It is possible that it's wearing. If you're seeing a difference in takeoff and climb rates for the same load, this is worth looking at.

It's also possible there is nothing wrong, and your brain is just noticing something that was there before as you've gained experience.

So, it might be worth some investigation, but if that doesn't turn anything up, then don't get paranoid and just keep on flying.
 
philiplane said:
A worn camshaft is the prime culprit in gradual loss of power when the compressions and all other indications are normal.
Click to expand...
I'm due for an annual. I think I'm going to get that checked this time around.

During my first year of ownership on my Tampico I kept getting worse and worse climb rates. When I got to annual I found out that I had a problem with the exhaust valve on the front left cylinder. We put in a rebuilt cylinder since I am getting close to an overhaul anyway.

The compression check will be a great place to start.

Jim
 
At work we fill out a trend sheet for cruse on each flight.

I've been keeping a little moleskin journal of my cruse setting in my plane, helps identify small problem before they become large problems.

Basically, get established into cruise, log the temp, OAT, rpm and manifold (in the case of pistons), fuel flow, IAS, hours on airframe, oil pressure and temp.
 
Kiddo's Driver said:
I'm due for an annual. I think I'm going to get that checked this time around.

During my first year of ownership on my Tampico I kept getting worse and worse climb rates. When I got to annual I found out that I had a problem with the exhaust valve on the front left cylinder. We put in a rebuilt cylinder since I am getting close to an overhaul anyway.

The compression check will be a great place to start.

Jim
Click to expand...

What do you cruise at?
I am around 95 most of the time.
 
You still thinking about upgrading to a faster plane?
We're getting a little more serious about swapping for a 20 or 21
 
SixPapaCharlie said:
Today was cool (mid-high 80s).

Yea right, you must have moved your plane way north if it was cool yesterday, It was extremely muggy. LOL I bet the DA was way up yesterday, are you sure that's not part of what you are experiencing?
Click to expand...
 
for a power check with fixed pitch prop, check your ma xstatis rpm sitting on the ground. There should a book acceptable range for your engine/prop combination.

If it's low and compression is ok, on your 320 check mag timing first, ignition harnesses next, then valve lift.
 
tecprotb said:
SixPapaCharlie said:
Today was cool (mid-high 80s).

Yea right, you must have moved your plane way north if it was cool yesterday, It was extremely muggy. LOL I bet the DA was way up yesterday, are you sure that's not part of what you are experiencing?
Click to expand...

Haha Ok cool is a relative term.
it wasn't cool but it wasn't a Texas summer day.
I thought DA yesterday was around 2100.

When I think high, I think of 3600 on super hot days.
Click to expand...
 
Timing was adjusted in May. Not sure about points.
 
SixPapaCharlie said:
Timing was adjusted in May. Not sure about points.
Click to expand...

We used to have to reset points every couple thousand miles to keep them right. Go through the mags, set everything correctly, clean and gap the plugs and see where you stand. Also check the dwell at the correct gap, the cams in the mags wear out and it throws off the dwell.
 
I would look at upgrading the exhaust. There's just not much there to go wrong.
 
Worn out? As in what component

I'd be more concerned about things compression than TT on that engine.
 
Henning said:
We used to have to reset points every couple thousand miles to keep them right. Go through the mags, set everything correctly, clean and gap the plugs and see where you stand. Also check the dwell at the correct gap, the cams in the mags wear out and it throws off the dwell.
Click to expand...

We have slick mags on the O-320-D2A. Not many people have the tools to open the slicks.

Speaking of mags, what is their history? Mine were new in 1998 and had right around 500 hours on the when I had the 500 hour "inspection" done to them last year. (The 500 hour inspection is dang near a rebuild.) I can't find any record of anything internal being done to them in the 500 hours, but I suspect there is something that is supposed to happen in there. (Probably what Henning is talking about in the quote.)
 
tecprotb said:
I would look at upgrading the exhaust. There's just not much there to go wrong.
Click to expand...

There is much chance of "upgrading" anything on a Tampico without going the Field Approval or one off STC route. They only imported about 65 of them into the U.S. so there is little financial incentive to develop a fleet STC.

Norman said:
Good point. It wouldn't hurt to take a look and see if the internal baffles are blocking the outlet.
Click to expand...

I have one of those cheap Harbor Freight borescopes with a two foot line on it. I bet something like that could do a decent job of looking up inside of the exhaust. Brian, you can get one for less than $100.

Jim
 
It would seem to me that a loss of power would manifest itself by lower rpm in an engine turning a fixed pitch prop. If the prop is turning the same number of rpm, it's moving the same amount of air provided the prop hasn't changed. Worn cams or leaky valves manifest by decreased rpm for a given throttle setting.
 
A 25 or 50 RPM drop isn't easy to see on the tach when you're in the takeoff roll, but it can make a significant difference in performance. A 100-RPM drop will just about kill the takeoff altogether.

If that prop hasn't been dressed properly the thrust can fall off some. The blade's airfoil profile needs to be maintained, but many guys end up with a blunt leading edge because they don't want to file down the "back" (which is actually the front) of the blade to prevent bluntness.

Dan
 
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Not enough info. Total time important. Local mechanic probably much better source than Internet speculation and naval gazing.
 
How much weight have you and your dad gained over the last year?!?!

:)
 
If you can't see 25/50 RPM tach on a scale with 100 RPM a tenth of an inch wide, I'd worry about passing your next eye exam.

OK, for those who are already examining the timing, the carburetion, the compression, the position of the cabin heat valve ... and all the rest of it, and if you don't suspect that there is anything wrong with the tach (pretty reliable units) and IF the engine is making full static RPM with a fixed pitch prop ...

WHY WOULD YOU HAVE THE GUY DO ANYTHING ELSE? WHAT DOES THE STATIC RPM CHECK SHOW THAT FIXING THE MAGS OR THE FUEL HAVE TO DO WITH IT?

Thanks,

Jim
 
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weirdjim said:
If you can't see 25/50 RPM tach on a scale with 100 RPM a tenth of an inch wide, I'd worry about passing your next eye exam.

OK, for those who are already examining the timing, the carburetion, the compression, the position of the cabin heat valve ... and all the rest of it, and if you don't suspect that there is anything wrong with the tach (pretty reliable units) and IF the engine is making full static RPM with a fixed pitch prop ...

WHY WOULD YOU HAVE THE GUY DO ANYTHING ELSE? WHAT DOES THE STATIC RPM CHECK SHOW THAT FIXING THE MAGS OR THE FUEL HAVE TO DO WITH IT?

Thanks,

Jim
Click to expand...

He hit the nail right on the head....:yes:.....:thumbsup:
 
I flew a lot 2 days ago and RPM looks great.
Redline is 2700
Gave full power and it was at about 2400 RPM
Speed increased and at Vr RPM was near 2600
Rotated and Pitched to Vy and RPM stayed at ~2550
Leveled off and it went right to redline

I am starting to think it is part perception and part humidity.

I am going to re read up on humidity's affect on performance.
I did 2 flights one in the morning and I was climbing 1000 feet / min
I flew another around noon and it was so sluggish it was crazy

Temp was not that different (maybe 12 degrees) but the humidity was way worse on the later flight.

I understand density altitude as it relates to temp but all of my POH takeoff, climb calcs are based on pressure altitude which I find annoying since the ASOS tend to report in terms of density altitude.

I have been away from the books for a bit. I need to study again what the humidity does to performance and I need to go back and figure out how to get pressure from the other inputs.
 
SixPapaCharlie said:
I am going to re read up on humidity's affect on performance.
Click to expand...

Just like a rocket, an airplane's thrust from the propeller is a function of how much mass it can throw back to get an "equal and opposite reaction" of thrust forward. See Isaac Newton, three laws of motion.

So with air, you are throwing back O2, at atomic weight 32 (16 x 2) or nitrogen N2 atomic weight 28 (14 x 2). With humidity you are throwing back water vapor with atomic weight (H20) 18. Lots more thrust throwing back dry air rather than humid water vapor.

Jim
 
weirdjim said:
Just like a rocket, an airplane's thrust from the propeller is a function of how much mass it can throw back to get an "equal and opposite reaction" of thrust forward. See Isaac Newton, three laws of motion.

So with air, you are throwing back O2, at atomic weight 32 (16 x 2) or nitrogen N2 atomic weight 28 (14 x 2). With humidity you are throwing back water vapor with atomic weight (H20) 18. Lots more thrust throwing back dry air rather than humid water vapor.

Jim
Click to expand...

Also one must consider the HP output of the motor itself.. Even though it is making book value run up RPM numbers, all motors are rated on a standardized set of rules...

On the dyno, the correction factor is a worldwide standard calculation.. ALL data is corrected to

59f air temp
29.92 baro and
0 (zero) % humidity...

High humidity eats power..:yes:
 
Let me comment that every pilot needs a digital optical tachometer for cross checking the tach in the airplane.
I keep one in my toolbox at the hangar and a couple of times a year I will pull it out to check that the plane's tach is working properly. My tachs at 2400 indicated are off by 40 and 70 rpm respectively.

The 40 is a tolerable deviation but 70 is a significant power difference. I have grease pencil tick marks on the glass to show where the actual 2400 is.

Edit: And for the constant speed prop folks, I might add that when the engine is off the manifold pressure gauge can be calibrated against the reported altimeter setting on the AWOS. I find that most manifold pressure instruments are off, some significantly. Here a tick mark on the glass will help operate the engine more efficiently.
 
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Dr. O said:
Let me comment that every pilot needs a digital optical tachometer for cross checking the tach in the airplane.
I keep one in my toolbox at the hangar and a couple of times a year I will pull it out to check that the plane's tach is working properly. My tachs at 2400 indicated are off by 40 and 70 rpm respectively.

The 40 is a tolerable deviation but 70 is a significant power difference. I have grease pencil tick marks on the glass to show where the actual 2400 is.

Edit: And for the constant speed prop folks, I might add that when the engine is off the manifold pressure gauge can be calibrated against the reported altimeter setting on the AWOS. I find that most manifold pressure instruments are off, some significantly. Here a tick mark on the glass will help operate the engine more efficiently.
Click to expand...

Model recommendation please
 
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