Monitoring Engine Start with Full Bypass
10-08-2016, 06:47 PM
#1
Monitoring Engine Start with Full Bypass
Hi.
All of my jets have been top hatch with no bypass. Every engine start I have made has been with the fire extinguisher in my hand literally inches away from the turbines fod screen. More than once I have had to put out fires on startup. being prepared and having such access has allowed me to quickly put out fires before they caused any damage.
How do you monitor engine starts with a fully bypassed engine that has no hatch such as an Ultra Flash?
Does a setup like that make cooling with a blower mandatory for a modern engine such as the Cheetah SE?
Thanks,
Dom
All of my jets have been top hatch with no bypass. Every engine start I have made has been with the fire extinguisher in my hand literally inches away from the turbines fod screen. More than once I have had to put out fires on startup. being prepared and having such access has allowed me to quickly put out fires before they caused any damage.
How do you monitor engine starts with a fully bypassed engine that has no hatch such as an Ultra Flash?
Does a setup like that make cooling with a blower mandatory for a modern engine such as the Cheetah SE?
Thanks,
Dom
10-09-2016, 08:30 AM
#3
Dom,
I have mostly had jets with full bypass installations. In 17 years of turbine modelling I have never had a fire on start up or had to pull the trigger on an extinguisher. I had one momentary fire on an air start engine when it lost a bearing and the engine quit turning but I was still hooked up to air and just a quick blast put it out. I would first look at why you have had startup fires. I know you've been at this a long time and I mean no disrespect by that but in my experience both personally and with the people I fly with, fires on start up have been a very uncommon experience. If there is a fire in a bypassed install that is coming out of the tailpipe and doesn't blow out on its own a quick blast down the inlet will usually put it out assuming you've shut off the fuel as well. Other than a clear bypass like the old cai bypasses were I don't know any other way you'd see it though.
I have mostly had jets with full bypass installations. In 17 years of turbine modelling I have never had a fire on start up or had to pull the trigger on an extinguisher. I had one momentary fire on an air start engine when it lost a bearing and the engine quit turning but I was still hooked up to air and just a quick blast put it out. I would first look at why you have had startup fires. I know you've been at this a long time and I mean no disrespect by that but in my experience both personally and with the people I fly with, fires on start up have been a very uncommon experience. If there is a fire in a bypassed install that is coming out of the tailpipe and doesn't blow out on its own a quick blast down the inlet will usually put it out assuming you've shut off the fuel as well. Other than a clear bypass like the old cai bypasses were I don't know any other way you'd see it though.
Last edited by LGM Graphix; 10-09-2016 at 09:43 AM.
10-09-2016, 08:50 AM
#4
I watched BV training one of his new techs at FiF a few years ago, and as we know all of his airplanes are full-bypass. He said something like this:
1) these are my airplanes, not yours so you will follow MY rules (smile)
2) you will ALWAYS have a fire extinguisher within reach from where you start the engine
3) you will ALWAYS have the hand data terminal plugged in and monitor the startup.
It made quite an impression on me and I have always followed rules 2 and 3 with my jets. It turns out to be interesting because as you learn the pump voltages, RPMs and temp patterns from a "normal" start, you can start to see problems appearing before they get worse .. e.g. higher Pv indicating clogged filters or other fuel draw problems.
I've also seen a lot of guys, if they have any concern about a hot start (e.g. one failed start due to getting the fuel system primed), hold one hand near the fuel cutoff .. again the idea is to anticipate vs. react whenever possible.
In my experience with jets, almost 10 years now I've had to use the extinguisher twice on my own planes .. once on a hot start and once when a bearing seized right after starting. One of these incidents (the bearing) was an open install, one was a "quasi-full-bypass" meaning that the engine was surrounded by the bypass tube but it was open for about 1.5" at the back ... the bypass ended 1.5" before the bellmouth. This was a typical Yellow Aircraft recommendation.
BTW, I use CO2 since the mfrs I have talked to say that it is least likely to do any engine damage. Always wondered if that was the best choice.
I agree that in many cases a leaf blower will put it out if the fuel supply is cut off ... have seen dozens of engine fires on various event flight lines where that has happened. It is also very educational comparing how folks respond to fires (ranging from running around shouting "who has an extinguisher??!" to calmly cutting off fuel and putting it out).
In the fires I have seen, the full bypass seems to be a great asset on minimizing damage to other parts of the plane, and for quick extinguishing.
Dave
1) these are my airplanes, not yours so you will follow MY rules (smile)
2) you will ALWAYS have a fire extinguisher within reach from where you start the engine
3) you will ALWAYS have the hand data terminal plugged in and monitor the startup.
It made quite an impression on me and I have always followed rules 2 and 3 with my jets. It turns out to be interesting because as you learn the pump voltages, RPMs and temp patterns from a "normal" start, you can start to see problems appearing before they get worse .. e.g. higher Pv indicating clogged filters or other fuel draw problems.
I've also seen a lot of guys, if they have any concern about a hot start (e.g. one failed start due to getting the fuel system primed), hold one hand near the fuel cutoff .. again the idea is to anticipate vs. react whenever possible.
In my experience with jets, almost 10 years now I've had to use the extinguisher twice on my own planes .. once on a hot start and once when a bearing seized right after starting. One of these incidents (the bearing) was an open install, one was a "quasi-full-bypass" meaning that the engine was surrounded by the bypass tube but it was open for about 1.5" at the back ... the bypass ended 1.5" before the bellmouth. This was a typical Yellow Aircraft recommendation.
BTW, I use CO2 since the mfrs I have talked to say that it is least likely to do any engine damage. Always wondered if that was the best choice.
I agree that in many cases a leaf blower will put it out if the fuel supply is cut off ... have seen dozens of engine fires on various event flight lines where that has happened. It is also very educational comparing how folks respond to fires (ranging from running around shouting "who has an extinguisher??!" to calmly cutting off fuel and putting it out).
In the fires I have seen, the full bypass seems to be a great asset on minimizing damage to other parts of the plane, and for quick extinguishing.
Dave
Last edited by ww2birds; 10-09-2016 at 08:54 AM.
10-09-2016, 09:43 AM
#6
2) you will ALWAYS have a fire extinguisher within reach from where you start the engine
3) you will ALWAYS have the hand data terminal plugged in and monitor the startup.
I've also seen a lot of guys, if they have any concern about a hot start (e.g. one failed start due to getting the fuel system primed), hold one hand near the fuel cutoff .. again the idea is to anticipate vs. react whenever possible.
BTW, I use CO2 since the mfrs I have talked to say that it is least likely to do any engine damage. Always wondered if that was the best choice.
Dave
I couldn't agree more with you. Back when I started with turbines it was never a concern whether somebody had an extinguisher present and used the data terminal. At the last jet event I was at, I made a comment to the CD about how lax people were starting. I saw mulitple starts without extinguishers present, a few starts where all the hatches were on the jet and just waiting for the engine to start, and times with no data terminal hooked up. The engines have become so good that complacency has taken over in a lot of cases.
Even though my P70 and my Olympus will autostart without the need to have a data terminal hooked up I still make sure to always hook them up. I still use propane start and do not carry an onboard start canister so I need to hook up the propane anyway.
The biggest cause of wet starts is failing to turn off your fuel valve on shut down. I make a habit out of shutting down both with the transmitter and simultaneously turning off the fuel valve, I can honestly say in 17 years of turbine modelling I have never had a wet start.
As for extinguishers, CO2 is the best cost effective choice I think. Haletron from what I understand is a better choice but is very expensive. I still have a number of old Halon extinguishers I take with me.
Truth is, I worry less about a fire in a bypass install than a jet without one mostly because as you mentioned it contains the fire better and in the case particularly of starting with propane there is no chance of the fuselage filling up with propane on a missed start and then a woof throughout the fuse when you try again if all the propane hasn't aired out!
10-09-2016, 10:01 AM
#7
Dom,
Welcome back buddy! I hope to see you at a few events next year!
I agree with Dave's comments from Bob - in a full bypass installation, you have to be familiar with the normal startup process of your engine and monitor it closely - especially with a kero start engine.
I would recommend that you actually open up the bypass for the first dozen or so starts so you can get a handle on what your engine normally sounds like and what the readings are during a normal start. After that you can keep it buttoned up.
Finally, if you have a hung start in a kero start engine, you *have* to turn it nose down and drain the fuel out of the engine and clean it up out of the pipe and fuse. If you don't you are almost guaranteed to have a hot start and very likely a fire in the pipe or fuse...
Bob
Welcome back buddy! I hope to see you at a few events next year!
I agree with Dave's comments from Bob - in a full bypass installation, you have to be familiar with the normal startup process of your engine and monitor it closely - especially with a kero start engine.
I would recommend that you actually open up the bypass for the first dozen or so starts so you can get a handle on what your engine normally sounds like and what the readings are during a normal start. After that you can keep it buttoned up.
Finally, if you have a hung start in a kero start engine, you *have* to turn it nose down and drain the fuel out of the engine and clean it up out of the pipe and fuse. If you don't you are almost guaranteed to have a hot start and very likely a fire in the pipe or fuse...
Bob
10-09-2016, 10:09 AM
#8
Dave,
I couldn't agree more with you. Back when I started with turbines it was never a concern whether somebody had an extinguisher present and used the data terminal. At the last jet event I was at, I made a comment to the CD about how lax people were starting. I saw mulitple starts without extinguishers present, a few starts where all the hatches were on the jet and just waiting for the engine to start, and times with no data terminal hooked up. The engines have become so good that complacency has taken over in a lot of cases.
Even though my P70 and my Olympus will autostart without the need to have a data terminal hooked up I still make sure to always hook them up. I still use propane start and do not carry an onboard start canister so I need to hook up the propane anyway.
[snip]
I couldn't agree more with you. Back when I started with turbines it was never a concern whether somebody had an extinguisher present and used the data terminal. At the last jet event I was at, I made a comment to the CD about how lax people were starting. I saw mulitple starts without extinguishers present, a few starts where all the hatches were on the jet and just waiting for the engine to start, and times with no data terminal hooked up. The engines have become so good that complacency has taken over in a lot of cases.
Even though my P70 and my Olympus will autostart without the need to have a data terminal hooked up I still make sure to always hook them up. I still use propane start and do not carry an onboard start canister so I need to hook up the propane anyway.
[snip]
When kero start works, its no muss, no fuss, but when it doesn't, its a real PITA. I have had to send one brand-new engine back for a failed plug on the second start, and my flying buddies have had to do that with a number of their engines as well. In addition, all of us have had an number of kero-start engines that have needed a lot of "parameter tweaking" to make the starts both reliable, and "safe" from a flames standpoint.
Finally, I have had two kero-start engines toast pipes - one of them while being tweaked by the manufacturer's chief engineer, and that has *never* happened to me with a propane start engine...
Bob
10-09-2016, 10:14 AM
#10
I agree with the complacency issue, but not with the contention that the engines have become a lot better on startup. My experience with kero start is that it is actually a lot less reliable then propane start and when it does fail, the results can be really bad.
When kero start works, its no muss, no fuss, but when it doesn't, its a real PITA. I have had to send one brand-new engine back for a failed plug on the second start, and my flying buddies have had to do that with a number of their engines as well. In addition, all of us have had an number of kero-start engines that have needed a lot of "parameter tweaking" to make the starts both reliable, and "safe" from a flames standpoint.
Finally, I have had two kero-start engines toast pipes - one of them while being tweaked by the manufacturer's chief engineer, and that has *never* happened to me with a propane start engine...
Bob
When kero start works, its no muss, no fuss, but when it doesn't, its a real PITA. I have had to send one brand-new engine back for a failed plug on the second start, and my flying buddies have had to do that with a number of their engines as well. In addition, all of us have had an number of kero-start engines that have needed a lot of "parameter tweaking" to make the starts both reliable, and "safe" from a flames standpoint.
Finally, I have had two kero-start engines toast pipes - one of them while being tweaked by the manufacturer's chief engineer, and that has *never* happened to me with a propane start engine...
Bob
