Big Wheels Keep on Turnin'

[Forrest Barber]

Re: Big Wheels Keep on Turnin'

I think I wrote this up before, there is no data on the early cowls.
The F-19 was a total fiasco, I flew a few of the tests. It worked best with no cowling, I proved that by going for parts lots of times with no cowling. Basically we had an older Model 19 N66xxN here to paly with.
The brand new 0-200 was equipped on the F-19 prototype with no under engine baffle, they forgot about it.
The "mouth" under the prop was eliminated, a 69-50 prop from our Cessna 150 was used. ( factory forgot to order a prop) . We waited till we had a near 59 degree day and away we went, doing the climb & cooling tests, used a blast tube onto the oil screen area ( ala Cessna 150) . REMEMBER these ships were built uinder CAR 3 & 4a, not Part 23. She finaaly passed one day and we called Cleveland MIDO to come look, they did and signed her off. It is not rocket science and the F-19's I am sure have had trouble since.
My BC12D , N43533 , runs too cool very early in the Fall and has no problem in the Summer time. We get 90-100 on ground. 100W oil & MMO.
I would like to fly your ship sometime

[VictorBravo]

Re: Big Wheels Keep on Turnin'

I finally put a home-made water manometer (U-tube) in the T-craft and recorded some useful info today. Attached are 2 PDF files of the 2 test flights I did today attached to this e-mail. I flew from Whiteman and did three takeoffs to measure the delta P across my cooling system in actual climbs. My standard benchmark CHT reading is taken after I turn downwind in the pattern at 1000 AGL.

Then I departed the pattern and flew to Santa Paula. I took some readings on the manometer at cruise speeds. Unfortunately I was not smart enough to put an orifice in the manometer tubes... so the readings were swaying back and forth... and it took several tries to get a stable reading at each speed.

The only modification since last flight (other than the manometer) was that I installed the "cold weather" partial cover over the oil cooling hole (bottom case baffle) on the engine. The oil temps had been 140 or so on the last flight, leading me to believe my improved oil baffle was working too well, giving me low oil temps but robbing the cylinder cooling airflow of some delta P in the process.

Then I landed at Santa Paula and had lunch, and taped over some more of the oil cooling hole to test on the way back home. This left only 20% of the hole open.

What I would like to know from any real live engineers out there (that's you Hank) is whether the pressure differentials at the speeds I am using are enough to power a cooling system efficiently, or whether these differentials are far less than you would expect.

The manometer was calibrated in inches of water column up and down from a zero line in the middle. The high pressure side of the plenum pushed on the right side tube, forcing the water down into negative numbers. the low pressure side of the plenum was plumbed to the left manometer tube, allowing the water to rise into the positive numbers.

Please let me know if and what sense these numbers make to you guys. My overall impression is that covering over the oil cooling hole helped a little. The temps are a little less.

Forrest you can fly this ship anytime, I'd be glad to have your opinions of where it stands in the grand scheme of T-crafts.

Bill

[Forrest Barber]

Re: Big Wheels Keep on Turnin'

Thank u Bill, maybe we stumbled across something when we closed off the "mouth" in the nose cowl. Old Kenny said "Hell, why not, lets try it! " Even a blind squirrel can find a nut in the Winter time.

[VictorBravo]

Re: Big Wheels Keep on Turnin'

Attempted two test flights yesterday.

First flight instrumented with same manometer. Closed off another portion of the square oil cooling opening on the cowl because my oil temps are still low. Somewhere between 12 and 15% of the opening is open, the rest was covered. Three takeoffs and landings. CHT's after climbs to 1000 AGL (55, 60, 65 mph IAS) were a few degrees lower than their equivalents on the previous flights.

Parked in the runup area, and proceeded to install a small aluminum lip piece on the previously stretched lower cowl, using Ty-Raps and aviation grade duct tape. Re-started and was cleared out onto the active runway for takeoff.

Engine failed on takeoff roll, felt like fuel starvation. Engine ran at idle for a few seconds after takeoff aborted, enough for me to head to the first taxiway turnoff, but then failed again so I had to turn off into the dirt to clear the runway.

Restarted engine with one shot of prime, and it idled reasonably well for a couple of minutes, but then stopped again.

Pushed aircraft off taxiway and into parking, tied tail, primed and started it again. Again it ran at fast idle for 3-4 minutes, and stopped.

Forum member L-2 Gary was asked to come out and take a look, he's the local expert on Stromberg carburetors. We started it again, ran it at a fast idle, and he asked whether I had rebuilt the primer recently. I said no. He opened the primer while the engine was running, and t started to run rough, due to additional raw fuel being allowed into the manifold. He suggested I remove the primer and cap off the manifold and see if that solved the problem.

However, a leaking primer would create a "rich failure", and the symptoms I had on takeoff felt like a "lean failure".

There was at least 4 gallons in the tank, and no water was found when draining the gascolator immediately after the airplane was pushed off the taxiway.

The airplane ran well on the previous flight, which was within fifteen minutes of the failure.

Anyone have any ideas what causes this?

If I don't come up with a fix pretty damn quick, my beloved wife is rightfully going to start lobbying me to get another airplane, because this is the second engine failure on takeoff in this particular T-craft as well as the umpteenth project, small problem turning into a big problem, repair, rebuild, brainstorm modification, wings off, strut X-ray to prevent me from being killed, not flying for months at a time, etc. etc. as well. Two engine failures on takeoff that were totally benign on the runway, but now she's thinking the third failure will probably not be on the runway.

[dewhitaker]

Re: Big Wheels Keep on Turnin'

Bill, the simplest fix is to do as Gary suggested. Any leakage of the primer will cause stumbling and excessive fuel pouring out the bottom. Could be an intermittant problem. You will probably find it starts just fine with out the primer. Primers cause more problems than they are worth, especially if you live in a warm climate. Mine gave me fits right at the end of the flying season before the day of infamy strut grounding. Will probably disconnect mine before flying again this spring.

[flyguy]

Re: Big Wheels Keep on Turnin'

Quiting at idle is a different animal. I don't think checking the primer when it is running ok proves anything. It will make a good engine run rough. To check if it is a lean failure free up your primer and be readly to give it a squirt, as soon as it tries to quit. If it continues to run as you squirt fuel into the engine then you have a lean problem and it is specific to the idle mixure circuit, or something after the primer source. Something came loose or there is trash in there. Could be something else--running a few minutes and then quiting does suggests that it might be a fuel supply problem. Takes about that long to suck the level down in the carb. If that then I would look at the gascolator, flex fuel line, and finally for something coming loose in the tank valve. Besides, knowing your talents, you probably have fixed it by now.

Old engine parts fail, but you are right, it makes me nervous as a whore in church too.

Mine quit at midrange, Idle was OK.
Darryl

[Larry Lyons]

Re: Big Wheels Keep on Turnin'

If all else fails look inside the fuel line if you have any hose. I have had the inner separate from the outer and suck shut. No indication at all on the out side. Has happened twice to me. Good Luck, Larry

[Ron Coleman]

Re: Big Wheels Keep on Turnin'

Let's see now.
One cylinder gets really hot.
Change in airflow doesn't seem to solve the problem.
Two cylinders are not running hot.
Obviously not lean unless there is an air leak, crack in head, intake tube seals or the like.
Oil temps are not too high (check gauge). Suggests no massive failure like crank bearings. Does not eliminate tight piston pin or stuck ring in one cylinder.
Pumping primer kills engine. Should just make it run really rough before it stumbles to a gargling stop. Suggests rich mix flushes oil from cylinder wall suggesting ring sieze and sort of eliminates the intake leak probability.
High probability of carb problem because as I recall that carb failed on you a couple times before, leaving you with out power while over town. You got the carb fixed so that sort of minimizes that cause, maybe. Of course you could have a venturi out of position or broken causing a lean fuel flow to one cylinder or visa-versa- rare but it happens.
I would get a bore scope and check the cylinder walls on the suspect cylinder and check for scoring. Only have to pull the cowling and plug.
While doing that I would have a pro run a thorough check on the engine or else the next time I took off I would fly in tight circles around the airport.
I would also put car gas and MMO in the tank just for kicks. Drain what you don't use and stick it in your car when you have decided if it makes any difference. Don"t tell anyone so you don't get busted.
I bad cam lobe or valve train can make a cylinder run hot.

I feel for you..good luck

RonC

[VictorBravo]

Re: Big Wheels Keep on Turnin'

As of 7PM this evening, the gascolator screen was clean as a whistle.

Removed primer fitting from intake spider and installed AN pipe plug. Removed copper primer line from top of gascolator, need to go get an AN "cap" plug to seal that off.

Next trip to hangar will be removing the fuel supply lines and checking flow into a bucket. Larry THANKS for the idea on the flex hose inner lining, I'll look at that if I can find a way.

This carburetor has about 50 hours or less since a proper rebuild from a fussy mechanic who is an expert on those carburetors.

The failure on takeoff was not a "gurgling" or "spitting" or "surging" failure. It was a rapid smooth decrease in RPM and noise. When I pulled the throttle back the first time it still ran at a high idle.

Additional info: After Gary and I looked at it and played with the primer a few times, we started it again and I taxied it back across the airport to my hangar. Ran fine all the way there, 3-4 minute taxi. Before I shut it down I did a 15 second full power runup, expecting it to quit or slow down, but it didn't.

[flyguy]

Re: Big Wheels Keep on Turnin'

"It was a rapid smooth decrease in RPM and noise. When I pulled the throttle back the first time it still ran at a high idle."

That sounds more like fuel starvation, as in the fuel level in the carb being sucked down with insufficient flow in--

If you do have a lean condition, it is unfortunately that you guys just disconnected your quickest and easiest method of trouble shooting that problem.

Bummer that it is starting to sound like an intermitten problem.
DC

[Hank Jarrett]

Re: Big Wheels Keep on Turnin'

Sounds an AWFUL lot like the fuel line interior collapsing to me. The inner liner can close off the supply one minute, then open back up the next. It would act just like your description.
SCARY
Hank

[lfries]

Re: Big Wheels Keep on Turnin'

I've lost power twice on takeoff. I do like 6,000' runways. Each time was due to my not remembering to check that the valve was fully open (at the valve).
After the 2nd incident when checking for fuel flow and seeing how weak it was the light went off then I reached in and pushed the valve open with
my finger and we had good flow.

[VictorBravo]

Re: Big Wheels Keep on Turnin'

Sounds an AWFUL lot like the fuel line interior collapsing to me. The inner liner can close off the supply one minute, then open back up the next. It would act just like your description.
SCARY
Hank

Thanks for the vote Hank, I appreciate it. The "symptom" of how it failed SURE would be accounted for by a sudden restriction in the fuel flow. There's only one flex hose in the whole fuel system, gascolator to carburetor, so it will be removed immediately and looked at. I don't know how you'd check to see if the lining is loose unless it is way past obvious that you can see it from one end. I'll bend it back and forth looking through the ends and see if I can identify something loose. But if it is a "flap" of inner lining that comes loose, blocks the flow, then springs back into place... how could you test for that?

[Forrest Barber]

Re: Big Wheels Keep on Turnin'

Maybe follow the old AD on the fuel line, we roll a ball bearing down the line both ways several times while flexing.

[taylorcraftbc65]

Re: Big Wheels Keep on Turnin'

Maybe follow the old AD on the fuel line, we roll a ball bearing down the line both ways several times while flexing.

I never heard of that one, thanks for enlightening me Forrest. Brie