The devil is in the details, and that couldn’t possibly be more true than in the NTSB findings from the case of an accident earlier this year involving a Cessna 177RG that crashed near Grass Valley, California. Its sole occupant was killed when the airplane collided with a tree following loss of engine power in the traffic pattern at Nevada County Airport (GOO).
It all came down to one loose nut, according to the NTSB’s final report.
Power Loss in the Pattern
The flight departed Auburn Municipal Airport about 15 minutes earlier and climbed normally up to about 4,400 feet. Witnesses who heard the pilot’s transmissions told NTSB investigators that the pilot sounded calm and professional, giving no indication of engine trouble until he made a mayday call in the Nevada County traffic pattern.
Upon entering the left base leg for Runway 7, the pilot reported a total loss of engine power over the CTAF. Likely in an effort to find a clearing closer than the airport, the pilot diverted from the pattern. 60 foot trees tragically got the better of the attempt, though, separating the Cessna’s stabilator before the aircraft descended uncontrolled to the ground about a mile west of the airport. It came to rest adjacent to a roadway.
The 64-year-old pilot, who held a private pilot certificate with airplane single-engine land privileges, was fatally injured.
Maintenance Issues Identified
Following the accident, NTSB investigators found that a B-nut fitting on the fuel line leading into the fuel flow divider was more than a half turn loose. Blue dye staining consistent with fuel leakage was found around the fitting. Investigators found no impact damage to the fitting and no other mechanical issues that would have prevented normal engine operation.
Data recovered from a recently installed JPI engine data management system showed the engine was operating normally until the final seconds of flight. At that point, NTSB investigators said cylinder head temperatures and exhaust gas temperatures briefly spiked and then dropped rapidly, a signature consistent with a sudden loss of fuel flow.
The pilot declared an (engine out?) emergency w approaching his destination airport. The ground speeds on ADS-B Exchange leading up to the crash are noteworthy. R.I.P. to the pilot, and prayers to his family and friends.
— Aviation Accidents 🇺🇸 (@AviationSafetyX) May 2, 2025
Fatal Accident (1) – RBL Missions LLC Cessna 177RG… pic.twitter.com/M2cvtYrSiq
The airplane had its annual inspection just 10 days earlier and had flown about 2.5 hours since. During that inspection, maintenance personnel installed the engine monitoring system and fuel flow transducer. Even aside from that, though, regulations require inspectors to check engine lines, hoses and fittings for leaks and looseness during annual inspections.
The NTSB found that the probable cause was the improperly tightened B-nut fitting, along with an inadequate maintenance inspection that failed to catch it. Together, those allowed a fuel leakage to form that ultimately resulted in the aircraft’s total loss of engine power.
Lessons From a Small Part
The facts of the accident point to a specific mechanical failure, and the board’s findings are a tragic but good reminder of how seemingly minor details can have catastrophic consequences. Fittings like these are commonplace in GA aircraft and can easily be disturbed during maintenance. When improperly secured, they can loosen further under vibration and thermal cycling.
And of course, those specific fittings are hardly the only small details that impact the safety of flight.
The accident is a good reminder of the importance of thorough post-maintenance inspections and leak checks, particularly after work involving fuel system components. Even with advanced engine monitoring equipment on board, the data showed there was little warning before power was lost entirely.
For pilots, the event serves as a reminder that recent maintenance does not guarantee mechanical integrity, and that vigilance during preflight inspections remains critical. For maintenance professionals, the NTSB’s report reinforces a long-standing lesson: attention to basic practices, proper torque and independent verification are just as vital to safety as any of the more complex systems and technologies they deal with on the job.
It just takes one loose nut.
My beef is with the Annual inspections which I think cause more problems than they find. I’ve owned a 210 for 39 years and I can say that the majority of the times Post annual from dozens of different shops the aircraft is returned with some maintenance induced squawk. Taking the airplane apart after 60-70 hrs is overkill by a lot. It should be increased to every 2 years especially if it is hangared and flown under 150 hrs during that period.
Less maintenance is better. The annual inspection is too invasive and should be reduced to a much more limited scope that can be performed visually, without taking things apart. I wish AOPA would take this up with the FAA and work through policy making and legislation to simplify annual inspection requirements.
" The do not trust their God to rouse them a little before the nuts work loose"
Rudyard Kipling The Sons of Martha. Should be over the entrance to every maintenance shop.
I agree, light aircraft tend to be over maintained. I remember over 50 years ago talking with some Royal Australian Air Force Huey pilots about their helos. They reckoned when they went on exercise with the grunts and got them out of the clutches of the maintainers they were much more reliable.
Personally I’ve seen more problems in sailplane world from maintenance than lack of.
The folks that are addressing the Annual inspection issue are missing a point. The fitting was loose because a JPI was installed. Was that before, during, or after the Annual?
The use of torque seal would make inspecting the work done a lot easier. A&P mechanics should use it a lot more. Owners should insist that it is used to make it possible to better inspect the work.
Unfortunately, most pilots don’t take much interest in maintaining or learning about such things. If I just had a 100 hour done I would be down there before it was buttoned up and look and put my hands on everything that was done. You never know what you might find. The life you save might be your wife, son, or daughter.
My brother’s partner in their Cherokee was hopping to Orcas Island from Bellingham - you cut the power from takeoff to land. It’s a good thing. The updraft carburetor dropped off the engine on power reduction as there was not oven one bolt installed to hold it there. Immediately after an annual, of course. Amazing it didn’t fall during the run up. He simply declared and dropped it onto the runway. The good news is their repair shop took incredibly good care of them after that! (Besides the fact no one was so much as injured or even inconvenienced much.)
It’s not the annual. It’s ground running and performing a proper leak check. And never tighten a b nut finger tight and walk away. Have the proper wrench in hand to tighten it before walking away.
That’s not where the failure occurred. It happened at the flow divider which is downstream from the fuel flow meter.
Torque seal was used in my boss’s accident. The same B nut was 1/2 turn loose. My boss wound up with a broken back and confined to a wheelchair. He got a lot of money from the engine overhauler though. He was pretty messed up from a previous accident.