From: Mike Busch [mailto:mike.busch@savvyaviator.com]
Sent: Sunday, January 04, 2009 11:14 AM
To: Robert J. Miller
Cc: Walt Troyer
Subject: Re: FW: Over the Airwaves - Journal for the Proficient Pilot - January, 2009

 

I agree 100% with what Walt Troyer said (and I very seldom agree with Floridians <g>). That's exactly what I teach my students. The cooldown business is an OWT, but it is necessary to allow the turbo to spin down before removing its oil supply. Normally the spin-down occurs naturally during taxi-in, but if the engine is throttled-up just prior to shutdown (e.g., taxiing uphill or into a very strong headwind or making a tight wheel-locked turn), then a little spin-down time should be allowed before shutting the engine down to ensure that the turbo is not spinning without lubrication.

Walt, if you got 1500 hours out of the turbos in a 402 or 421, you're doing okay. The turbo overhaul guys tell me that typical turbo life is 1,000 hours. (I've typically gotten 1,500 hours per turbo on my T310R.)

Best...Mike
 

===============================================


Robert J. Miller wrote:

Mike:  I knew I was going to open a can of worms with this month’s OTA article on turbochargers.  (See http://overtheairwaves.com)

Do you have any comment on this reader’s points??

 

Bob

 

From: B25flyer@aol.com [mailto:B25flyer@aol.com]
Sent: Sunday, January 04, 2009 10:42 AM
To: rjma@rjma.com
Subject: Re: Over the Airwaves - Journal for the Proficient Pilot - January, 2009

 

In a message dated 1/4/2009 8:57:54 AM Eastern Standard Time, rjma@RJMA.COM writes:

http://overtheairwaves.com.



Bob

As usual a very good issue of OTA

One comment on your statement on turbochargers. I agree with the OWT on cooling. The question I have is one that might be different today with some of the design changes in TC by the manufacturers. With 1500 hours in 400 series Cessna, 402/421, it wasn't the cooling part that caused the problem it was the shutdown of the engine and no oil pressure to the TC shaft bearings.

I have seen TC engines shut down immediately after high power usage on the ground such as power and brakes to turn into a parking spot and then a immediate shut down. The TC is still spinning at a higher RPM but now has no oil pressure to the bearings and that is where the problem will be. In other words after using the high power wait 30 seconds for the TC to slow down to normal idle speed.

Here is an example of TC spinning with no oil pressure. Having been associated in some ways with the farm equipment business for many years TCs on new tractor engines could fail in as little as 20 hours of use on a newly delivered tractor. They found out that the problem was the air movement around the exhaust stack while the tractor was on a semi doing 70 MPH caused the the TC to turn with no oil. Next time you see new tractors being delivered on a semi look at the exhaust stack and you will see that it is either removed and there is tape over the outlet or it is taped or covered at the top.

Walt Troyer
5205 Oak Road
Sebring, FL 33875
P 863 471 1423