Joe Broady
Airman 1st Class
- 106
- May 30, 2019
I've been reading the report on the 2015 T-28 crash that killed David Tokoph. Shortly after takeoff from Las Cruces the engine failed and the plane went down in a field. It looks like a survivable crash: no fire, wreck is upright, and cockpit appears intact. However, Tokoph sustained serious head injury and died four days later. The NTSB report notes the shoulder harness had no inertial lock. It had to be operated manually.
Internally the engine was a mess. One cylinder had to be pried off to inspect the crankcase. Metal fragments had torn up the rods, pistons, and cylinder skirts. The no. 6 rod was broken. According to the report, the crash was due to "failure of the No. 6 cylinder connecting rod, due to improper rotation of the propeller during a previous hydraulic lock."
One of the witness statements in the accident docket came from the fueler, who "observed Mr. Tokoph trying to turn the 'prop' but it was not turning." It's not clear if he was pulling the prop through or trying to crank the engine with the starter. (The statements were taken by a cop, not an accident investigator.) Tokoph asked for a ground power unit. After it was hooked up, it took three attempts to keep the engine running. The fueler said the first two attempts, the engine died about 10 seconds after the GPU was unplugged. Also, its sound was different between GPU plugged in vs. unplugged. I have a hard time understanding why external power would make a difference once the engine was running.
Another Interesting observation by the fueler was that the engine would "piss a lot of fuel" during the start attempts. Could that have been due to excessive priming draining from the blower?
The NTSB docket contains a 2000 Avweb article, "Radial Engines and Hydraulic Lock" by Rick Durden. I already knew about removing a plug from each of the lower cylinders, but I had never heard of running the engine briefly with plugs out.
NTSB accident report
accident report docket
Internally the engine was a mess. One cylinder had to be pried off to inspect the crankcase. Metal fragments had torn up the rods, pistons, and cylinder skirts. The no. 6 rod was broken. According to the report, the crash was due to "failure of the No. 6 cylinder connecting rod, due to improper rotation of the propeller during a previous hydraulic lock."
One of the witness statements in the accident docket came from the fueler, who "observed Mr. Tokoph trying to turn the 'prop' but it was not turning." It's not clear if he was pulling the prop through or trying to crank the engine with the starter. (The statements were taken by a cop, not an accident investigator.) Tokoph asked for a ground power unit. After it was hooked up, it took three attempts to keep the engine running. The fueler said the first two attempts, the engine died about 10 seconds after the GPU was unplugged. Also, its sound was different between GPU plugged in vs. unplugged. I have a hard time understanding why external power would make a difference once the engine was running.
Another Interesting observation by the fueler was that the engine would "piss a lot of fuel" during the start attempts. Could that have been due to excessive priming draining from the blower?
The NTSB docket contains a 2000 Avweb article, "Radial Engines and Hydraulic Lock" by Rick Durden. I already knew about removing a plug from each of the lower cylinders, but I had never heard of running the engine briefly with plugs out.
NTSB accident report
accident report docket