Ground run-ups of TSIO-520 series engines often occur during the process of adjusting the turbocharger, the propeller governor, or the fuel injection system. The top cowl is usually removed.
Ground runs at high power ( with the cowl removed ) increase the probability of cracked cylinder heads. The cooling air is not adequately being directed around and down through the cylinder head fins. The result is uneven cooling which causes damaging thermal stress in the cylinder head casting. It can happen quickly.
The correct procedure for ground running an engine is the temporary installation of a partial top cowl, with only the aft portion removed. Such a configuration allows for access to make adjustments to the turbocharger and fuel injection systems.
Partial / fabric run-up top cowls are available and sold through RAM. See Engine Run-up Cowl.
The RAM fabric run-up cowling fits Cessnas: T310/320, 340/A, 402B, 402C, 414 and 414A.
If you must,
RAM advises the following run-up limits when the top cowl is removed:
- Extreme Caution is essential anytime an engine is being run-up on the ground.
- At all times 400°F CHT and 200°F oil temperature are maximum allowable.
- Looking for fuel or oil leaks, limit run-up to two minutes maximum and 1200 rpm.
- Testing adjustments to fuel injection system or turbocharger should not be done
with cowling off.
- With left nose cowl off to adjust the governor, limit 1 to 4 seconds at high power.
- Cowling installed and cowl flaps open, no time limit within reason, keeping in mind
that 400°F CHT and 200°F oil temperature is maxi-mum allowable.