NTSB Opens Docket on Reno Air Race Crash

[440_Magnum]

Re: NTSB Opens Docket on Reno Air Race Crash

I could stare at the telemetry data for hours, its that fascinating to me.

The first thing that grabbed me (though I don't think it has anything to do with the accident at all) was a sudden drop in engine oil pressure (orange trace) at about time index 1621:20. It didn't go dangerously low, but it interests me because it was an abrupt change in pressure that didn't correlate to an abrupt change in MAP, RPM, G loading, or engine oil temp. Anyone have any idea what would cause that in a Merlin? I can envision a similar drop with an increase in MAP just because the jump in torque could force various clearances to open up slightly as the block and crank distort, or a similar change with increasing temp as the oil thins. But that change is just all by itself in the data. Struck me as odd.

[spacegrrrl]

Re: NTSB Opens Docket on Reno Air Race Crash

I finally got in and read it all. Sadly it will seem to come down to some improper bolts and cross threaded lock nuts attaching the pitch actuator.

Shows how at the speeds the planes fly at the smallest thing can go wrong and make it all hit the fan.

The reduction of power a little before the incident makes me wonder if Jimmy was starting to feel some of the low frequency flutter that preceded the event.

Also thought it was interesting that many folks reported that the Ghost flew with the tab in trail at race speed when it clearly didn't. Photos showed at race speed it was displaced "up" to push the elevator slightly "down".

The fuselage twist was pretty crazy. Does anyone know if the other Mustangs do the same thing at speed?

Even though it seem like we can say at this point we "know" what happened there is still going to be so much we will never really know for sure.

Was it just me or did seeing some of the high resolution photos remind you of just what a sleek racer the Ghost was?

Also I'd forgotten Skips Pirep for the other racer being so sensitive to trim at speed.

Spacegrrrl

[xmh53wrench]

Re: NTSB Opens Docket on Reno Air Race Crash

^^^^^^
No offence, but....huh???

[Propellerhead]

Re: NTSB Opens Docket on Reno Air Race Crash

The fuselage twist was pretty crazy. Does anyone know if the other Mustangs do the same thing at speed?

Spacegrrrl

RR III used to exhibit oil canning in the tailcone.

I've never seen it in Voodoo or Strega. I don't know if it's lighting conditions, masked by paint schemes or it just doesn't happen to them. I've got plenty of Strega belly shots where the wing structure can plainly be seen telegraphed through the sheet metal at speed.

In non-Mustang land, you can see it on Dread up in the cowling and the Bear all through the tail like crazy. Dimple city.

[Mluvara]

Re: NTSB Opens Docket on Reno Air Race Crash

I could stare at the telemetry data for hours, its that fascinating to me.

The first thing that grabbed me (though I don't think it has anything to do with the accident at all) was a sudden drop in engine oil pressure (orange trace) at about time index 1621:20. It didn't go dangerously low, but it interests me because it was an abrupt change in pressure that didn't correlate to an abrupt change in MAP, RPM, G loading, or engine oil temp. Anyone have any idea what would cause that in a Merlin? I can envision a similar drop with an increase in MAP just because the jump in torque could force various clearances to open up slightly as the block and crank distort, or a similar change with increasing temp as the oil thins. But that change is just all by itself in the data. Struck me as odd.

The NTSB will likely discuss some of this when they present the probable cause.

FYI - There are two ways to measure temperature. First is into the cooler and second is out of the cooler. If the system is a radiator with a spray bar, one will likely see a temperature increase of the oil or coolant coming out of the radiator if the temp of the fluid coming into the cooler (out of the engine) increases. If the cooler is a boiler, unless the boiler cannot handle the state change of the fluid in the cooling process, you will see a relatively constant temperature until the heat transfer cannot be absorbed. Thus, boilers are nice because you get a nice constant temperature out of the system.

[AirDOGGe]

Re: NTSB Opens Docket on Reno Air Race Crash

...The reduction of power a little before the incident makes me wonder if Jimmy was starting to feel some of the low frequency flutter that preceded the event...

Spacegrrrl

I believe some reduction in power is common when coming off the back straight, the fastest part of the track, into that oh-so-sharp turn.

[xmh53wrench]

Re: NTSB Opens Docket on Reno Air Race Crash

I finally got in and read it all. Sadly it will seem to come down to some improper bolts and cross threaded lock nuts attaching the pitch actuator.
Spacegrrrl

Sorry, I was on my phone earlier and could only make a limited response.

Your sentence sounds like a conclusion.
As far as I know the NTSB has not published one.
There is nothing that I read in the report (granted I have not read ALL of it...I am working on it) that would support such a statement.
If there is could you please reference it here or PM me.

Thanks...

[51fixer]

Re: NTSB Opens Docket on Reno Air Race Crash

I saw some pics , what's up with those parallel indentations on both wings ???? Aero flexing ? In one pic they are on both, then later only on one . ( the pics are showing the top of the Wing).

Wing had structure added and built up to replace the removable gun and ammo doors. The added structure flexes and moved different than the original structure. The wings were under extreme g induced loads at that moment and the added structure is evident in the photo. Probably not that significant considering.

[51fixer]

Re: NTSB Opens Docket on Reno Air Race Crash

The NTSB will likely discuss some of this when they present the probable cause.

FYI - There are two ways to measure temperature. First is into the cooler and second is out of the cooler. If the system is a radiator with a spray bar, one will likely see a temperature increase of the oil or coolant coming out of the radiator if the temp of the fluid coming into the cooler (out of the engine) increases. If the cooler is a boiler, unless the boiler cannot handle the state change of the fluid in the cooling process, you will see a relatively constant temperature until the heat transfer cannot be absorbed. Thus, boilers are nice because you get a nice constant temperature out of the system.

Stock the temp probes are reading fluids out of the engine. Stock it is in the R/H wheel well for coolant going to the radiator and close to the engine in the oil out of the engine line. Some have an additional coolant temp probe added where the coolant exits the head going to the header tank. We don't have anything to read temps going out of the cooler, radiator or going into the engine.

[51fixer]

Re: NTSB Opens Docket on Reno Air Race Crash

I found the part regarding stick force per G very interesting! Early P-51D's loaded a certain way, at a certain airspeed would go negative stick force after x amount of G. I.E. You have to push forward to relax. Compound that with an airplane at the aft C.G. limit (also destabilizing), unknown bob-weight size, elevator weights way bigger than stock, etc.

Regardless of what caused the crash, it seems this airplane must have been a serious handful when everything was working "normal". I was pretty impressed with most of the documents.

A/C was more than an inch forward of aft limit of CG. This is the FAA TCDS civilian CG. The military operated at further aft CG loading than this. I was actually surprised it wasn't loaded further aft, at or just aft of the limit at full depart the ramp weight.
I know people who operate without the bob weight and I have never heard of stick reversal. Military CG loading could have an impact on this. Early horizontals also had a different angle of incidence with fabric covered elevators.

[Race5]

Re: NTSB Opens Docket on Reno Air Race Crash

RR III used to exhibit oil canning in the tailcone.

I've never seen it in Voodoo or Strega. I don't know if it's lighting conditions, masked by paint schemes or it just doesn't happen to them. I've got plenty of Strega belly shots where the wing structure can plainly be seen telegraphed through the sheet metal at speed.

In non-Mustang land, you can see it on Dread up in the cowling and the Bear all through the tail like crazy. Dimple city.

If I remember correctly, RRIII did not have the vertical stabilizer offset removed like Strega and Voodoo.

[Sparrow]

Re: NTSB Opens Docket on Reno Air Race Crash

If I remember correctly, RRIII did not have the vertical stabilizer offset removed like Strega and Voodoo

.

RR's tail was indeed straight. Coolant temp is sensed coming out of the engine either off the A bank outlet fitting or, in the wheel well as Rich said. Oil temp is usally taken at the tank after the oil cooler. If one was reading oil outlet temps in the cockpit, they might be a bit shocked. Stockers run generally 5 to 10 degrees different between inlet/outlet temps. At race power, the differential is much higher.

Sparrow

[51fixer]

Re: NTSB Opens Docket on Reno Air Race Crash

.

RR's tail was indeed straight. Coolant temp is sensed coming out of the engine either off the A bank outlet fitting or, in the wheel well as Rich said. Oil temp is usally taken at the tank after the oil cooler. If one was reading oil outlet temps in the cockpit, they might be a bit shocked. Stockers run generally 5 to 10 degrees different between inlet/outlet temps. At race power, the differential is much higher.

Sparrow

Your right on the oil. I guess I need to drink more before replying.

[Sparrow]

Re: NTSB Opens Docket on Reno Air Race Crash

Your right on the oil. I guess I need to drink more before replying.

No worries, must be that "other" time zone thing-----

[spacegrrrl]

Re: NTSB Opens Docket on Reno Air Race Crash

Sorry, I was on my phone earlier and could only make a limited response.

Your sentence sounds like a conclusion.
As far as I know the NTSB has not published one.
There is nothing that I read in the report (granted I have not read ALL of it...I am working on it) that would support such a statement.
If there is could you please reference it here or PM me.

Thanks...

In one of the final docs - Aircraft Performance 13 - Study in section "E. CONCLUSIONS"

A low amplitude flutter of the left trim tab due to loosening screws and a growing fatigue crack in one of the screws attaching the trim tabs could have increased in amplitude and cyclically loaded the control rod until it failed, causing the left roll and pitch up.

Look through the documents and photos again and the screws including a mention of cross threaded nuts (even a photo in there somewhere) are referenced several times. So yes, not my conclusion, the NTSB's in that doc. So reading all the docks before jumping on someone in the forums is a good idea.

Spacegrrrl