The pilot departed Salinas Municipal Airport (KSNS) in California, en route to Livermore Municipal Airport (KLVK) after an uneventful prefight check and engine run-up.
About 30 minutes after takeoff, he noticed that the Cessna 177RG’s engine monitor was indicating an increase in EGTs for all cylinders. The engine then briefly “stuttered,” and he decided to divert to an airport en route for a precautionary landing.
He then adjusted the fuel mixture control and the temperatures returned to normal, so he decided to continue to the original destination.
About 10 minutes later, he initiated the landing descent to KLVK by reducing engine power and moving the fuel mixture to full rich.
During the landing approach, the EGTs again began to rise, and the engine lost all power.
The airplane sustained substantial damage to the left wing and stabilator after landing short of the runway and striking a set of instrument landing system lights.
Post-accident examination did not reveal any anomalies with the engine or airframe, and the engine could be operated at varying speeds during a ground run.
Review of the data recorded by the airplane’s engine monitor indicated that the EGT rise was about 200° F, and during the periods of EGT rise, there was no discernible change in fuel flow. (The fuel flow transducer was installed at the inlet of the fuel injection servo, rather than the outlet to the flow divider.)
The airplane was equipped with a Bendix RSA-5AD1 fuel injection servo. The servo and flow divider were tested and examined at Precision Airmotive’s facility. The testing revealed that both units met the performance specifications required following a field overhaul.
However, disassembly of the fuel injection servo revealed significant internal corrosion and corrosion deposits throughout. The diaphragm cavities displayed “water lines” and corrosion on the metered and unmetered fuel sides, consistent with water contamination (figures 1 and 2).
Corrosion deposits were present in the servo valve seat cavity and in the mixture control assembly (figures 3 and 4).
Precision Airmotive Service Bulletin PRS-97, revision 2, issued in August 2013, stated that the time between overhaul (TBO) for all fuel injection system components is either the same as the TBO specified by the engine manufacturer for the engine or 12 years since placed in service or last overhauled, whichever occurs first. The bulletin also stated that an overhaul is mandatory if the fuel system is contaminated with water.
Maintenance records indicated that the last rebuild of the fuel injection servo was performed in August 1999, 23 years before the accident, while the engine was undergoing an overhaul.
Another engine overhaul was performed in August 2012, and the corresponding logbook entry stated that no accessories were overhauled at that time.
The maintenance logbooks did not indicate the fuel system had been exposed to water, however examination of the airplane indicated that the gascolator had recently been replaced.
There was no maintenance entry to reflect this work, and the mechanic who performed the most recent annual inspection stated that he did not replace the gascolator at that time.
There were no significant periods of inactivity noted in the logbook, although the owner stated that the airplane sat idle for six months before he purchased it in June 2020. He stated that the airplane was kept in a hangar for much of its recent life.
Probable Cause: The total loss of engine power due to an inadequately maintained fuel injection servo.
To download the final report. Click here. This will trigger a PDF download to your device.
This July 2022 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
This correlates with many used aircraft postings where the seller claims, “Engine past TBO but compressions are great, and engine runs smooth”. There are many more components to an engine including the integrity of the case itself, and this story proves that compressions are only a small part of engine health. How do I know? Flew a Grumman AA1A a few years ago with a fresh top and 1900 hours total time on the Lycoming 0235 which has a TBO of 2,400 hours. The engine was running like a top during a cross country when suddenly it didn’t as the engine seized due to a spun crankshaft bearing. The spinning bearing became so hot that it welded itself to the crankshaft and created a preferred dead stick (less drag– no windmilling situation). Happy ending as I was able to glide 7.5 miles to a fly in community and land without a scratch. So much for sellers inferring that compressions on a high time engine are a sure sign of entire great engine health. Buyer beware as I have questioned sellers regarding this type of scenario at which time and in many cases, they become highly indignant and defensive.
Reading the full report, the only thing I can see that this pilot could have done was to pull the prop to increase his glide. With the prop set for cruise through full forward, it behaves like a speed brake with the engine windmilling.
This is a very compelling story, but there are so many of them it would seem that buying a used GA aircraft poses a real and present danger to the new owner/pilot. Used to read a lot of stories of bad vacuum pumps; burned valves; broken connecting rods, losely torqued connecting rod nuts, and on and on and on. Quite a few of these result in death.
Can anyone invent a protocol / procedure for suspecting and detecting hidden internal rot and decay waiting with a little red devil with a pitchfork ready to carry you to hell in a smoking crater? Other than a complete engine teardown and minute component inspection of everything internal like this servo, how can you know? It’s insidious, like cancer left undetected eventually takes you to the cemetery. I don’t have an answer. Does anyone else on this list have a practical suggestion?
Thanks/Regards/J
My thoughts are that when buying an aircraft, have a competent A&P with AI, that you know, to go over the engine and airframe log books.
Look for recently replaced items that may suffer an ‘infant failure’. New parts can have a higher failure rate that parts with 100’s of hours on them.
Then look for items that are at or past their inspection interval.
In this case the fuel servo was well past the 10 year inspection/ rebuild/ overhaul time , and the ‘more than 28 days out of service’ time frame, and should have set off a loud alarm bell.!!!
Talk with the mechanic/ company that last worked on the aircraft. What did they do, and maybe not do that was recommended.
Piston engines are very reliable, as long as they are maintained per the manufacturer’s instructions, manuals, service bulletins, ADs…
So, water in the fuel at some time ago. And, no info on when and why the gas collator was replaced. Maybe it was full of water and was also corroded ?
Precision Aeromotive has a number of service instructions on preserving the servo if it is out of service for more than 28 day….
So, the mechanic that worked on the aircraft missed servicing the fuel system!
It also looks like that there is no way to flush the fuel side of the servo, so disassembly looks like that only way to ensure that it’s free of any contaminants.
Carburetors have a bowl drain plug, that allows the carb to be flushed of any grit or water.