Boeing 737, related to previous post of unlucky mechanic...

[rreis]

Hi all

I was at Tegel, Berlim, awaiting to fly to Brussels and watched how a B737 from KLM reverse into the runaway, towed by a duty car (probably not the proper name for it but I hope you understand. It's a car with a harm attached to the landing gear to pull/push the aircraft around). There was one man inside the car and other outside, connected to the 737 by cable. This cable was connected to the aeroplane in the right side, bellow the cockpit. That recent post about the guy sucked inside an engine is still fresh in my head and so I thought if this cable connection has anything to do with it. Can someone throw some light into it?

thanks!

rreis

[warbirdcrew]

Panel to which your guy was attached is the communications panel for the groundcrew to talk to the flightcrew. The cable you saw was his headset cord. It's routine procedure for him to be there (been there many times myself). If you look closely there should be a red line painted on the fuselage between him and the engines which marks the edge of the suction danger zone.

[rreis]

oh, thx for the explanation. From where I was standing I didn't see that red line (besides being a little colorblind). It makes sense because next I was about to ask what kind of mechanical device would be able to shut down the engine so fast to prevent the disaster (is there any such device? How fast can a jet engine be shut down?)

[warbirdcrew]

As far as I know, the Boeing 737 book says engines are to be avoided for 30 seconds after shutting off the engine in order to allow it to spool down and the suction danger to go away.

[warbird1]

oh, thx for the explanation. From where I was standing I didn't see that red line (besides being a little colorblind). It makes sense because next I was about to ask what kind of mechanical device would be able to shut down the engine so fast to prevent the disaster (is there any such device? How fast can a jet engine be shut down?)

What warbird crew is referring to is what we have here in North America. I don't know if the EU has the same exact painted danger zones, but I'm sure they have something similar.

As far as shutting down the engine, you can move the start lever to cutoff immediately, but as mentioned, it does take some time for the engine to spool down. I'm afraid that if the pilot were to get notice that someone was being sucked into an engine, it would already be too late due to the lag in response time.

[rreis]

As far as shutting down the engine, you can move the start lever to cutoff immediately, but as mentioned, it does take some time for the engine to spool down. I'm afraid that if the pilot were to get notice that someone was being sucked into an engine, it would already be too late due to the lag in response time.

Yes, I thought so. At least normal shutdown will have some lag due to inertia. I was wondering if there was (or ever was idea of) some sort of way to stop one of those engines FAST even if destroying it in the process (and saving someone live)

[warbird1]

As far as shutting down the engine, you can move the start lever to cutoff immediately, but as mentioned, it does take some time for the engine to spool down. I'm afraid that if the pilot were to get notice that someone was being sucked into an engine, it would already be too late due to the lag in response time.

Yes, I thought so. At least normal shutdown will have some lag due to inertia. I was wondering if there was (or ever was idea of) some sort of way to stop one of those engines FAST even if destroying it in the process (and saving someone live)

I don't think you could save someone that quick. If someone gets sucked in, it's going to be very fast, probably less than a second. Even if a groundcrew was in direct communications with the pilot, it would still take more than a second to react and shut the engine down. Those engines aren't cheap, they are at least 1 Million USD, probably more a piece. It's not worth developing such a system because it would be ineffective and even if you destroyed it, the person sucked in would already be dead, in addition to the cost of destroying the engine plus the cost of the system itself, along with the developmental costs, FAA approval, etc. It's basically impractical to design such a system.

[The Inspector]

The CFM equipped 37's all have prominent decals on the fan cowls that show the exclusionary zone around the inlets, it's 14 feet with the engine @ idle, the decal is a glypf of a human form in a red circle and a diagonal line across the person and the circle as well as a picture of the engine and a red exclusionary semi-circle around the inlet end of the decal with all the usual things FKIA's don't read like 'stay out' 'extreme danger'.
The vehicle you are referring to rresi is called a tug with a tow bar, the usual procedure is to 'push back' with the hydraulics turned off so the NLG can pivot for sharp turns while pushing back, then after given the 'all clear' by the person on the headset, the crew turns on the hydraulics. Turning the pumps on with the tow bar attached could (and usually does) cause the NLG to snap to centered up and could (and has) busted the towbar.
Many years ago @ KSEA, a NORTHWEST ORIENT 727 (hows that for some time ago?) was being pushed back on a nasty dark Winter evening, the guy on the com headset after clearing the crew that the towbar was off and the nose steering knuckle was reattached, slipped on some ice, fell down and knocked himself out when his head hit the cement. The airplane taxied away, went to the end of the runway and put the coals to it, on rotation the #3 engine fire warning went off along with a loss of power, the airplane crew secured the engine, circled and landed. While this was going on in the air, someone noticed the poor ground guy laying on the ramp and they hauled him off to the airport emergency room still unconscious. When they looked @ the #3 engine they discovered the extermly long ground com cord snaked up over the top of the right wing and found the chewed up headset in the first several stages of the engine.
You'd be amazed at how far away from the inlet on a 'classic' 737-200 during engine trims an old, weak JT8 can suck in a medium sized bird like a Crow or Robin, nor how quickly it can do that.

[Cking]

the usual procedure is to 'push back' with the hydraulics turned off

The 737's I work on have a steering bypass valve in the nose u/c bay. After the tow bar is disconnected you remove a flagged pin from it, tell the pilot you have done it and, after retreating to a safe distance hold it above your head un till the pilot gives you the "Thumbs up"
The bit I don't like about this is you have to get into the bay while the tow crew are pulling away and if there is a mix up and the pilot taxies off, you are basicaly in front of the nose gear with no quick way out!
I did hear that the early 737-1/200's didn't have the steering bypass valve fitted, hence the "Hydraulics off" towing.
All boeings and Airbus's now have bypasss valves

weak JT8 can suck in a medium sized bird like a Crow or Robin, nor how quickly it can do that.

I used to work with a guy who had been ingested by a "Weak" JT8 He lost is right forearm and was badly brused!


Rgds Cking

[The Inspector]

I used the term 'weak' in comparison to the monsters now hanging on wings like the 4084, TRENT, and CF-90 (17000 # thrust vs. 145000 # thrust). The average JT8 inlet is about 35 inches in diameter, a CF-90's is 13&1/2 FEET in diameter. you might choke out a JT8 depending on how you hit the inlet, but you'll be strip steak out the back of the big ones like the pictured CFM.
The key thing here is have great respect for any aircraft engine piston or turbine.

[rreis]

many thanks for the input, it has been instructive

[Cking]

I used the term 'weak' in comparison to the monsters now hanging on wings.

Appologies if you thought I was criticising, I was not.

a CF-90's is 13&1/2 FEET in diameter..

A friend of mine said he thought he could squeeze him self between the blades of a GE90-110 on a 777-300ER. I bet him a pound that he couldn't and bet him another pound that if he did he couldn't get back out again before I got into the flight deck and tried to start the engine!!! He declined, spoil sport

The key thing here is have great respect for any aircraft engine piston or turbine.

Well said. Check everything, then check again and get your mate to check too. Nobody died of double checking,

Rgds Cking