Jet Crash and fireball?
06-28-2015, 04:27 AM
#1
Jet Crash and fireball?
Hey guys I was talking to my jet mentor yesterday about the sad loss of his Skymaster 2m viper.
He has flown this sexy jet for 2 years now many times useing a kingtec k100 on diesal fuel.
He said he was doing a fly buy and had a brief lock out (wings rocked with no commands given), so he set up to land and he said it did it again on the base leg, but once he had it lined up to land it just rolled over and crashed about 30 feet up.
Yes he is useing Spectrum Powersafe 12 channel receiver with DX18, 2 6.6 life packs with 2 jr switches, and a Deamon Cortex gyro.
After the crash everything tested just fine with no drama, he thinks he was haveing TX lock out as he thinks the turbine was off before hitting the ground because there was no large fireball, as the fuel tank ruptured and there was diesel fuel everwere.
But as I understand Diesel is only flamible under pressure. So if you were useing diesel fuel would that decrease the chance of a fireball crash?
He thinks it might of been the gyros falt, but how would you test your equipment afterwards?
The motor and everything but the fuse is fine, but how do you know what to blame in this situation? I got the gyro from him as he don't even want to mess around with it and he likes his power box gyros better.
Can you send in the cortex for testing?
Is diesel fuel safer in a crash?
I thought our tubes turn them selfs off if there is a loss of signal for more than a second, so I thought the motor would of turned off the first time he thought it had signal loss.
What would you do in this situation?
He has flown this sexy jet for 2 years now many times useing a kingtec k100 on diesal fuel.
He said he was doing a fly buy and had a brief lock out (wings rocked with no commands given), so he set up to land and he said it did it again on the base leg, but once he had it lined up to land it just rolled over and crashed about 30 feet up.
Yes he is useing Spectrum Powersafe 12 channel receiver with DX18, 2 6.6 life packs with 2 jr switches, and a Deamon Cortex gyro.
After the crash everything tested just fine with no drama, he thinks he was haveing TX lock out as he thinks the turbine was off before hitting the ground because there was no large fireball, as the fuel tank ruptured and there was diesel fuel everwere.
But as I understand Diesel is only flamible under pressure. So if you were useing diesel fuel would that decrease the chance of a fireball crash?
He thinks it might of been the gyros falt, but how would you test your equipment afterwards?
The motor and everything but the fuse is fine, but how do you know what to blame in this situation? I got the gyro from him as he don't even want to mess around with it and he likes his power box gyros better.
Can you send in the cortex for testing?
Is diesel fuel safer in a crash?
I thought our tubes turn them selfs off if there is a loss of signal for more than a second, so I thought the motor would of turned off the first time he thought it had signal loss.
What would you do in this situation?
Last edited by mikes68charger; 06-28-2015 at 04:32 AM.
06-28-2015, 12:02 PM
#5
Actually, its not, its the vapor above the liquid fuel that burns.
JetA, Diesel, and Kerosene are so close, I don't think there is any significant difference in their flash points. As Rich said, the fuel has to be "atomized" in order to ignite. It also has to have a source of ignition, and for JetA, Diesel, K-1, it has to be an especially hot source - like an engine that is already running, or is at least still hot enough to be in the glowing red state. If it is not, then there is *much* less chance that the fuel will ignite. That is why its important to shut the engine down before impact. Even just a few seconds off and the engine parts (i.e., turbine wheel, tail cone, etc.), will have cooled enough to keep from igniting the fuel...
Bob
JetA, Diesel, and Kerosene are so close, I don't think there is any significant difference in their flash points. As Rich said, the fuel has to be "atomized" in order to ignite. It also has to have a source of ignition, and for JetA, Diesel, K-1, it has to be an especially hot source - like an engine that is already running, or is at least still hot enough to be in the glowing red state. If it is not, then there is *much* less chance that the fuel will ignite. That is why its important to shut the engine down before impact. Even just a few seconds off and the engine parts (i.e., turbine wheel, tail cone, etc.), will have cooled enough to keep from igniting the fuel...
Bob
Last edited by rhklenke; 06-28-2015 at 12:08 PM.
06-28-2015, 01:58 PM
#9
Mike
06-28-2015, 03:21 PM
#10
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Turbine could be shut down and cooled off but a shorted battery will also start a kero fire after a crash. Saw one this last week and had it happen to me back in the day at Mich Jets.
06-28-2015, 04:48 PM
#11
It generally doesn't result in the "fireball" right after impact though - its usually some black or grey smoke followed by flames... Equally destructive though if you can't get to the airplane on time. I've seen the same thing with gas-powered airplanes as well.
Bob
06-28-2015, 06:10 PM
#12
Did he check the aileron servos? It could have been one going bad. They normally fail in a set position but you never know. Just from what you describe that could have been the cause. It appears no vertical change until it rolled over. So it appeared the elevator may have been still working.
The only other thing to find out would be to check the ECU for signal loss causing the turbine to shut down if that is what happened it couldn't have been the Cortex.
I fly the same setup in most of my jets. I have met a fellow pilot who experience a short lock out due to the failsafe receiver. The first time he got it home he told me one side would no longer power up. Later in the same jet ( a viper) the receiver shut down completely. He wanted to warn me last year and I am always checking for both lights on the receiver before I fly. I have not had a problem but you know the saying everything that is built by a human can and will go bad.
The only other thing to find out would be to check the ECU for signal loss causing the turbine to shut down if that is what happened it couldn't have been the Cortex.
I fly the same setup in most of my jets. I have met a fellow pilot who experience a short lock out due to the failsafe receiver. The first time he got it home he told me one side would no longer power up. Later in the same jet ( a viper) the receiver shut down completely. He wanted to warn me last year and I am always checking for both lights on the receiver before I fly. I have not had a problem but you know the saying everything that is built by a human can and will go bad.
06-28-2015, 08:58 PM
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You can read the Xicoy ECU with the GSU data terminal and it will tell you if the reason for the last shutdown was a user command (i.e. trim tab down) or loss of signal/power. That might or not might tell you anything. Atomization of the fuel is key to the fuel exploding on models as with full size jets. Kero and diesel are less volatile and dangerous than gasoline but regardless - impact hard enough, you will get a fine mist of fuel and a spark or any surface above the ignition temp will cause the entire cloud of atomized fuel to ignite. Essentially the same thing that the nozzles do inside the combustor when you are flying.
Greg
Greg
06-29-2015, 03:28 AM
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Actually, its not, its the vapor above the liquid fuel that burns.
JetA, Diesel, and Kerosene are so close, I don't think there is any significant difference in their flash points. As Rich said, the fuel has to be "atomized" in order to ignite. It also has to have a source of ignition, and for JetA, Diesel, K-1, it has to be an especially hot source - like an engine that is already running, or is at least still hot enough to be in the glowing red state. If it is not, then there is *much* less chance that the fuel will ignite. That is why its important to shut the engine down before impact. Even just a few seconds off and the engine parts (i.e., turbine wheel, tail cone, etc.), will have cooled enough to keep from igniting the fuel...
Bob
JetA, Diesel, and Kerosene are so close, I don't think there is any significant difference in their flash points. As Rich said, the fuel has to be "atomized" in order to ignite. It also has to have a source of ignition, and for JetA, Diesel, K-1, it has to be an especially hot source - like an engine that is already running, or is at least still hot enough to be in the glowing red state. If it is not, then there is *much* less chance that the fuel will ignite. That is why its important to shut the engine down before impact. Even just a few seconds off and the engine parts (i.e., turbine wheel, tail cone, etc.), will have cooled enough to keep from igniting the fuel...
Bob
Here are the flash points of the fuels we use:
Diesel 126° F
Jet A, Jet A1 107.6° F
Kerosene 100° F
Gasoline -45° F
Temperature above the flash point will cause evaporation and increase the chance of a fire. Looks like diesel is the safest from this standpoint.
06-29-2015, 06:54 AM
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Yep, that's a risk - especially with LiPo's...
It generally doesn't result in the "fireball" right after impact though - its usually some black or grey smoke followed by flames... Equally destructive though if you can't get to the airplane on time. I've seen the same thing with gas-powered airplanes as well.
Bob
It generally doesn't result in the "fireball" right after impact though - its usually some black or grey smoke followed by flames... Equally destructive though if you can't get to the airplane on time. I've seen the same thing with gas-powered airplanes as well.
Bob
