According to the pilot, the flight in the experimental Raptor Junior 540 departed Santa Monica Airport (KSMO) in California, en route to Camarillo Airport (KCMA), in Camarillo, California, to conduct touch-and-go landings.
About five miles southeast of KCMA, he noticed a warning indication on the airplane’s avionics display alerting him to a loss of electrical power. He stated that within seconds, the entire display, excluding the Dynon Primary Flight Display, which had a backup battery, “went blank,” followed by a total loss of engine power.
He performed emergency procedures to restore electrical and engine power but was unsuccessful.
He performed a forced landing to an agricultural field about 4.5 miles southeast of KCMA, during which the airplane sustained substantial damage. The pilot was seriously injured in the crash, while a passenger sustained minor injuries.
The airplane was equipped with an electronic fuel injection and ignition system, manufactured by EFII Systems. Electrical system redundancy was accomplished by use of a main and auxiliary system, with two independent batteries and an alternator. The system shared a common ground line that connected the negative terminals for both batteries and was routed through a ground bus located behind the nose cone bulkhead to the engine compartment and engine case.
Post-accident examination of the wreckage revealed that the ground feed-through stud that connected the battery ground terminals to the ground bus was loosely connected on the nose cone bulkhead. The feed-through nut was 3.5 turns loose, which corresponded to approximately 3.5 threads of the feed-through stud.
Additionally, neither a spring lock washer nor a secondary locking nut were present on the feed-through stud assembly, as was found on all other primary electrical connections throughout the airplane.
Probable Cause: A total loss of engine power due to the loss of power to the electronic fuel injection and ignition system, which was the result of a loose connection between a common ground feed-through stud and the ground bus.
To download the final report. Click here. This will trigger a PDF download to your device.
This January 2024 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.
Apple changed word. It’s magneto
Something to be said for the mechanical magnify
JimH. I am a know nothing but in my boat I have two batteries and have a switch where I can determine which battery to use. I use one to run the large gas engine and the other for the small electric trolling motor.
Is something like that in operation here?
A textbook example of a single point of failure. Sheesh!
I use very few metal stop nuts, and I can’t remember where they are used on my old Cessna ?. Maybe in the engine compartment where a nylock nut is not allowed due to the high temps.
Where do you use them ?
Certainly any where near heat, the engine. My A&P said he had seen some nylocks let loose before, so he wanted me to swap out the original tail feather hold down 10-32’s in my RV-3. It first flew 11/2/85. All of the nylocks were tight as I replaced each. Kent Rockwell did a great job and used the good stuff when he built it. My guess is my A&P had seen some nylocks that were reused and never trusted them again.
Short answer, wherever I can.
Geewhiz! We’ve departed age of simple reliability and entered the age of overly-engineered unreliability. One nut, one wire can cause complete devastation? No thanks.
For lack of a lock washer….. Wow.
From page 6 of the Airframe and Engine Exam Report,
“ Disassembly of the feed through stud assembly revealed that a single tooth lock washer had been used, rather than both a tooth lock washer and spring lock washer as had been found with all other primary electrical connections “.
Figure 4 on the same page and Figure 5 on page 7 show a single tooth lock washer.
For clarity I would have written “ one internal teeth lock washer “.
https://www.aircraftspruce.com/catalog/hapages/lockwasherstars.php?clickkey=9485
The lock washer was there.
No pictures were shown of the other primary electrical connections, with two types of lock washers.
I did not know that using both types of lock washers was needed. How many lock washers does an electrical nut need ?
12 hours on their new Berkut, bummer. It was some great piloting to be able to survive that off field landing.
As an electrical engineer, pilot and aircraft owner, I don’t understand using 2 batteries in parallel, as shown in the wiring diagram. Each has a battery relay , which needs to be closed for the alternator [ 1] to recharge each battery.
Why not use one larger higher AH capacity battery ?
I’ve never seen a battery fail internally, unless it was very old, more than 5 years. They usually lose AH capacity and can’t supply the starter with enough amps to crank the engine, so get replaced.!
Then, there is the 2 , single points of failure; one ground cable from the jumpered batteries. and it looks like one wire from the jumpered positive sides to the main buss.
Separate wires don’t add much weight and adds redundant reliability.!
So, one loose battery connection caused an off airport landing and sever damage.!!
Hi Jim,
Please see my comment above. I’d be sincerely interested in your thoughts. I’m just an ex manufacturing engineer.
An internal tooth lock washer is normally used on small diameter machine screws, A split lock washer can be used for the size bolt shown in the pic. Using both on a bolt is usually not done.
But, the bolt is too long and it should be a fully threaded bolt, not as shown, needing 4 washers to get the nut torqued.
The ring terminal on the wire should not be bent at an angle. The flat washer and lock washer may not fully seat on the terminal. [ no washers under the ring terminal ]
Push on terminals are not a good idea for any connection , A screw type terminal strip is better with individual screws for each wire.
Some push on terminals have a hole in the center , along with the wire terminal. So, a safety wire can be attached, but care to not short to any adjacent terminals !
Also, the plastic plate should not be used. It will compress over time, causing the connection to loosen and vibration causing the nut to back off.
A also worked as a manufacturing engineer on computer room line printers with Data Products Corp…..noisy beasts !!
Thank you for the reply Jim, I concur. The extra flat washers looked wrong to me as well. This is the first time I had ever heard of using two lock washers.
I like MS-21042 Jet Nuts for my little red plane.
https://www.aircraftspruce.com/catalog/hapages/ms21042.php
I use them often. Although I saw recently they are not being made as well as they used to be, here in America … where I have heard that before.
Best Regards,
Glenn