Skywest hot start

Wait, this isn't the Batmobile???
MATTEL_60's_BATMAN_FIGURE_ANNOUNCEMENT_02.jpg
 
"...plane seems okay now"

Thanks, Captain Twitter.
 
So the APU caught fire or the engine itself? RJs have hot start prevention?
 
Velocity173 said:
So the APU caught fire or the engine itself? RJs have hot start prevention?
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Judging by the pic, I'd say tailpipe fire vs "hot start". A number of years ago a buddy of mine had a very similar start up fireball while parked right next to me (we were starting up together).....even 100 or so feet away, with the canopy open and my arm on the rail, I could feel some pretty intense heat. It wasn't actually a "hot start" (no unusual EGT rise), just a surprising and self correcting tailpipe fire. It was a really cold day (20-ish degrees F), and he didn't crank the motor long enough to get the motor and air going through it warmed. So I guess failure to atomize the fuel or something and it all just started pooling in the tailpipe until finally it lit off, which it most certainly did. Luckily he knew to cut the throttle, keep cranking and blow it out rather than blow the fire bottles. It was quite a show for us and the plane captains/maintainers though!
 
That is not an APU fire.

Those engines are probably only about $1.2m exchange.
 
35 AoA said:
Judging by the pic, I'd say tailpipe fire vs "hot start". A number of years ago a buddy of mine had a very similar start up fireball while parked right next to me (we were starting up together).....even 100 or so feet away, with the canopy open and my arm on the rail, I could feel some pretty intense heat. It wasn't actually a "hot start" (no unusual EGT rise), just a surprising and self correcting tailpipe fire. It was a really cold day (20-ish degrees F), and he didn't crank the motor long enough to get the motor and air going through it warmed. So I guess failure to atomize the fuel or something and it all just started pooling in the tailpipe until finally it lit off, which it most certainly did. Luckily he knew to cut the throttle, keep cranking and blow it out rather than blow the fire bottles. It was quite a show for us and the plane captains/maintainers though!
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Lol! That would get the heart rate up.

Does the Hornet have hot start prevention or do you have to cut manually? The GEs in the 60 have it. Never Had one but had plenty of compressor stalls on start up in Astan though. Hot start prevention won't work in that situation so at some point you have pull the PCL off to keep from over temping. Had a fire balls come from the APU occasionally from over priming as well.
 
Not a turbine guy. Can someone explain what happens in a hot start or tailpipe fire or whatever? Seems like fuel isn't atomized or is making its way out the back and catching fire but how does that happen?
 
petrolero said:
Not a turbine guy. Can someone explain what happens in a hot start or tailpipe fire or whatever? Seems like fuel isn't atomized or is making its way out the back and catching fire but how does that happen?
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Well this is a turbine helo explanation so don't know how accurate it is for FW. A hot start generally happens when the fuel has pooled in the combustion chamber after shutdown and wasn't purged properly with compressor (P3) air. Or, you could have a weak battery and its not spinning the NG section fast enough to sustain start. Or, you could be at high altitude and trying a dual engine start and the APU can't provide enough air to spool up the NG fast enough for start. Or, like I said above, you can get a compressor stall (loud popping) where the airflow isn't going from front to back but reverse. In that case, if you don't cut the fuel, she'll generally go right thru redline.

In the turbine helos that I've flown, generally they have what's called an ECU or electrical control unit or even a FADEC that has an ECU. Anyway, what it does is it monitors several inputs, one of which is temp (TGT, MGT, TIT) to make sure it doesn't exceed a predetermined level on start up. If it does, the ECU has authority to cut the fuel on its own. In theory that's what is suppose to happen but in practice, on rare cases I've had friends who had a hot start because the temp rose so fast the ECU couldn't cut fuel in time. The ECU also has the power to prevent the engine from over speeding but that's a whole other discussion.

Hopefully that explaination covers the FW hot start description as well.
 
Velocity173 said:
Well this is a turbine helo explanation so don't know how accurate it is for FW. A hot start generally happens when the fuel has pooled in the combustion chamber after shutdown and wasn't purged properly with compressor (P3) air. Or, you could have a weak battery and its not spinning the NG section fast enough to sustain start. Or, you could be at high altitude and trying a dual engine start and the APU can't provide enough air to spool up the NG fast enough for start. Or, like I said above, you can get a compressor stall (loud popping) where the airflow isn't going from front to back but reverse. In that case, if you don't cut the fuel, she'll generally go right thru redline.

In the turbine helos that I've flown, generally they have what's called an ECU or electrical control unit or even a FADEC that has an ECU. Anyway, what it does is it monitors several inputs, one of which is temp (TGT, MGT, TIT) to make sure it doesn't exceed a predetermined level on start up. If it does, the ECU has authority to cut the fuel on its own. In theory that's what is suppose to happen but in practice, on rare cases I've had friends who had a hot start because the temp rose so fast the ECU couldn't cut fuel in time. The ECU also has the power to prevent the engine from over speeding but that's a whole other discussion.

Hopefully that explaination covers the FW hot start description as well.
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Yes that helps a lot. Thanks!
 
That would ruin your day for sure.
 
Since I know Nauga loves TF-30s...:D
 

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I've seen a recip tail pipe fire but never a jet one. That looks very toasty!

I wonder if it burned the tail cone any beyond just wiping off the soot.
 
Wonder if the ramp guy even remembered the correct hand signal for FIRE ? Next I wonder if the flight deck crew recognized it ?
 
Plane caught fire after pilot turned on its engine
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Well there's the problem right there. Stupid pilot turned on the engine. Pilot error for sure!
 
Another cause (not that it was the case here....I know the Captain and he's pretty sharp), is initiating the start sequence without the ignition armed. Fuel is introduced and just pools in the engine. When you don't get a start you begin looking for the problem. You then notice you didn't arm the igniters! AVOID THE INTINCTIVE IMPULSE TO TURN THEM ON! Either an explosion or fire is almost guaranteed!

Proper procedure is to cut off the fuel and continue to dry motor it to blow out/dry out the pooled fuel, respecting starter time limits.

THEN arm the igniters and go through a normal start sequence.
 
petrolero said:
Not a turbine guy. Can someone explain what happens in a hot start or tailpipe fire or whatever? Seems like fuel isn't atomized or is making its way out the back and catching fire but how does that happen?
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To add a little FW flavor to the great response from McFly, tailpipe fire =/= hot start, at least in the "there is something wrong with that motor" troubleshooting discussion in maintenance control. With a hot start, you see an unusually rapid rise in EGT as the motor is starting to spool up to idle. A true hot start will exceed design limits if the fuel is not terminated.

With a tailpipe fire, typically there are no cockpit indications, as it is so far aft in the motor that it doesn't tend to trip an EGT spike, and any engine fire sensor circuitry is typically mounted externally around the motor or in the engine bay.....so since it is contained IN the engine, it won't trip that warning either. It does tend to be very startling for anyone nearby or potentially in the cockpit itself.

So you could say it is semantics, but I guess the difference is where in the engine that the overheat happens. The only things I've seen cause a hot start are either 1) a malfunctioning fuel control unit, or 2) a strong wind blowing into the tailpipe (which will restrict normal flow on startup). Tailpipe fire is almost always due to pooled fuel, something that is causing an airflow problem through the motor, or a heavy cloud of fuel that for whatever reason has not atomized and ignited in the combustion chamber. You can have tailpipe fires of a different nature in afterburner equipped aircraft, but I'd say that is the main cause.

I'll caveat this all by saying that most of my experience is in afterburning low bypass turbofans, so there is probably some difference with non-AB high bypass motors just due to geometry, flow, and some of the ancillary components. Hope that answers your question.
 
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Velocity173 said:
Lol! That would get the heart rate up.

Does the Hornet have hot start prevention or do you have to cut manually? The GEs in the 60 have it. Never Had one but had plenty of compressor stalls on start up in Astan though. Hot start prevention won't work in that situation so at some point you have pull the PCL off to keep from over temping. Had a fire balls come from the APU occasionally from over priming as well.
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Yeah, it was like 0600 in the AM, and I was both trying to wake up as well as not freeze to death before I got my first motor online and could close the canopy........sure woke me up!

Legacy Hornet (what I was in at the time) does not have any hot start prevention, as it is a mechanical/electric fuel unit not FADEC. I have seen a number of APU fires, normally from just not waiting for the thing to cool down and drain residual fuel between subsequent starts.......that and at dusk, there often is a slight flame that comes out when it lights off. Had that one time, and a very junior plane captain under instruction. He immediately started throwing me the fire signal and I dutifully blew the fire bottle. I was pretty new at the time and also didn't realize it was probably a false alarm. Luckily my mistake was rectified because the fire bottles turned out to be empty......thus not requiring all the extra maintenance/engine drop......at least until they figured out the bottles were empty and a mx investigation ensued :)
 
LDJones said:
Another cause (not that it was the case here....I know the Captain and he's pretty sharp), is initiating the start sequence without the ignition armed. Fuel is introduced and just pools in the engine. When you don't get a start you begin looking for the problem. You then notice you didn't arm the igniters! AVOID THE INTINCTIVE IMPULSE TO TURN THEM ON! Either an explosion or fire is almost guaranteed!

Proper procedure is to cut off the fuel and continue to dry motor it to blow out/dry out the pooled fuel, respecting starter time limits.

THEN arm the igniters and go through a normal start sequence.
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haha surprise!
 
petrolero said:
Not a turbine guy. Can someone explain what happens in a hot start or tailpipe fire or whatever? Seems like fuel isn't atomized or is making its way out the back and catching fire but how does that happen?
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Obviously seeing as though it's August in North America, this isn't the issue, but....
I have heard of similar occurrences in the winter. Just a few drops of dew that fall to the bottom of the inlet can freeze the fan. You can fry an engine in an instant if that happens.
 
Kritchlow said:
Obviously seeing as though it's August in North America, this isn't the issue, but....
I have heard of similar occurrences in the winter. Just a few drops of dew that fall to the bottom of the inlet can freeze the fan. You can fry an engine in an instant if that happens.
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Except that you do not add fuel and ignition until you have at least positive rotation of the fan. Besides, in the winter part of the pre-flight should include spinning the fan by hand to make sure it rotates.
 
LDJones said:
Another cause (not that it was the case here....I know the Captain and he's pretty sharp), is initiating the start sequence without the ignition armed. Fuel is introduced and just pools in the engine. When you don't get a start you begin looking for the problem. You then notice you didn't arm the igniters! AVOID THE INTINCTIVE IMPULSE TO TURN THEM ON! Either an explosion or fire is almost guaranteed!

Proper procedure is to cut off the fuel and continue to dry motor it to blow out/dry out the pooled fuel, respecting starter time limits.

THEN arm the igniters and go through a normal start sequence.
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Yep. I knew a guy sitting at the FE panel on an L-1011 who happened to notice that the ignition circuit breakers were out during a start where there was no light off but lots of fuel flow. Rather than waiting for the captain to abort the start then do a dry motor, he pushed the breakers in. It lit off in spectacular fashion.
 
Kritchlow said:
Obviously seeing as though it's August in North America, this isn't the issue, but....
I have heard of similar occurrences in the winter. Just a few drops of dew that fall to the bottom of the inlet can freeze the fan. You can fry an engine in an instant if that happens.
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:goofy::goofy::goofy::goofy:

Sorry I laughed hard at this one.:yes:
 
"Wait.. you didn't turn on the ignit......" POOOOOOF..
 
Are you guys sure about this ignition issue? I am typed in 4 jets and flown 3 other turboprops (and nowhere current in all of them), but I am about 100% sure I never touched the ignition switches during start in any of them. The start sequence took care of it always and then turned them off. All I had to do was remember to introduce fuel at XX% RPM and wait for light off at another higher %. If light off didn't occur then you did some other things, doubtful that throwing ignitions on manually was one of them. Again this is from my fading memory has it has been many years since I flew some of the types.
 
Mark, I am not typed in any jet but I am an A&P who has worked for the airlines and have been run/taxi qualified on a few types (L-1011, 727, 737, 757). Typically, the ignition selector switch do not have an off position but have a three position switch where you select one of two igniters or both, i.e. L-Both-R or A-Both-B, etc. This helps to prevent the issue described. Where you get into trouble is when you were trying to start on L(A) or R(B) only and it doesn't work and you switch to the other or both. You also get into trouble when the CBs were pulled and it wasn't caught until fuel was applied and there was no light off. The best thing to do after applying fuel if there is no light off within the allotted time is to shut off fuel but leave the starter engaged to blow it out without exceeding the starter duty cycle. Then try another start with the ignition selector in the proper position.
 
SkyDog58 said:
Except that you do not add fuel and ignition until you have at least positive rotation of the fan. Besides, in the winter part of the pre-flight should include spinning the fan by hand to make sure it rotates.
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It doesn't work that way for all airplanes. Sometimes N2 is spinning fast but no N1 yet. Can't wait too long with N2 too high to introduce fuel.
Also, many airplanes you cannot spin the fan by hand. Even if possible, the conditions you would do it are not advisable. If the wing had water or glycol on it for example.
 
Getonit said:
Are you guys sure about this ignition issue? I am typed in 4 jets and flown 3 other turboprops (and nowhere current in all of them), but I am about 100% sure I never touched the ignition switches during start in any of them. The start sequence took care of it always and then turned them off. All I had to do was remember to introduce fuel at XX% RPM and wait for light off at another higher %. If light off didn't occur then you did some other things, doubtful that throwing ignitions on manually was one of them. Again this is from my fading memory has it has been many years since I flew some of the types.
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Can only speak for the CRJ. You arm either ignition A or ignition B, which automatically fires when certain rotation parameters are met. You then disarm (turn off) the ignition after start. You can go through the entire start prices and introduce fuel without arming them.
 
LDJones said:
Can only speak for the CRJ. You arm either ignition A or ignition B, which automatically fires when certain rotation parameters are met. You then disarm (turn off) the ignition after start. You can go through the entire start prices and introduce fuel without arming them.
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Same with the DC-9, except there are 3 different types of ignition switches (3, 4 and 5 position switches). If you don't turn it on to start, you'll never get one running.
 
Getonit said:
Are you guys sure about this ignition issue? I am typed in 4 jets and flown 3 other turboprops (and nowhere current in all of them), but I am about 100% sure I never touched the ignition switches during start in any of them. The start sequence took care of it always and then turned them off. All I had to do was remember to introduce fuel at XX% RPM and wait for light off at another higher %. If light off didn't occur then you did some other things, doubtful that throwing ignitions on manually was one of them. Again this is from my fading memory has it has been many years since I flew some of the types.
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If you do the before start correctly, you'll need to get the ignition somewhere. In the CRJ, you just select A or B ignition, and then run through the starting sequence and like you said basically during the start, all you do introduce the fuel and watch it do its thing.

I've seen more than one guy reach up during a starting sequence after he realized he forgot to arm an ignition and poof. I've been that guy.

I watched some mechanics on a CRJ-200 do this very thing and it looked a lot like the picture.
 
Different airplanes have different levels of automation during start. I have flown several that have auto sequence but can also be done manually. Heck, I flew one electric start airplane that depending on the temperature we would put the batteries into series for the start (cockpit switch). Fadec airplanes usually pretty automated.
 
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