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There have been some gruesome deaths involving ground staff being sucked into jet engines, presumably because the engine thrust was set well above idle. Are there safety features (besides prudence on the flight deck) that are designed to mitigate this risk?

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No, there are no safety features. Only safety procedures on the flight deck and on the ground.

Basically it all boils down to that nobody may go near any aircraft (jet or prop; they are both similarly dangerous) that may have engines running. When starting the engines, the pilots first turn on the beacon (the red flashing lights on the belly and tail), then check the ground crew has left and only then start the engine(s). And similarly upon landing, the pilots shut the engines down, wait a bit to let them spool down and turn off the beacons; then the ground crew should ask (via radio or the wired intercom connected to a socket at the nose) whether the engines are indeed off and only then they may start working.

Since start-up normally only happens after push-back, so away from the terminal, there is usually no risk then. Upon arrival however the ground crew needs to come to the aircraft relatively quickly and insert chocks to the wheels, so the correct procedures are important.

Here see a recent accident where ground worker was injured because the procedures were not followed (he was coming from the rear, so he was only blown away, not sucked in).

In that incident, the engines were at idle. They are still very dangerous in that case. I found an Airbus document which shows danger areas, for A320 with CFM56 engines, at idle as:

  • suction danger 2.2m (7.2ft) from engines (semicircle forward and to the sides of the engine and back to 1.5m behind the inlet) and
  • exhaust danger to 55m (180ft) behind the nozzles with 30° spread with exhaust velocity exceeding 105km/h (65mi/h) for 17m (55ft) aft of the nozzles.

At full power the suction area grows to 5.9m (19.5ft) radius and the exhaust danger to 275m (900ft) with velocity over 105km/h down to 150m (500ft) aft.

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Ground operations are complicated and dangerous. You can find some details about risks and hazard zones associated with operations on the ground, here.

Precautions taken to minimize risk are (among others:)

  • Everyone must be clearly visible. Ground personnel always wears high visibility clothes including high visibility vests, and trousers with high reflectivity stripes (even during the day.) The tarmac is well lit. Operations cease on extremely low-visibility situations.

  • Cockpit to ground communications: The ground will inform the cockpit that they are cleared to start-up the engines. The ground crew will make sure that no person or object is in the hazard zones of the aircraft.

  • A special indicator light will be on when the engines are about to be started/are running (for example: the Anti-Collision light for the B737, and the Beacon light for the A320.)

  • Jet blast deflectors are used where necessary. This went infamously wrong in this instance.

  • The spirals painted on jet-engine spinners are used as visual cues from the ground crew that the engine is on (this is somewhat anecdotal: the spiral on a spinner that is slow-spinning because of the wind will be still visible as a spiral but the spiral becomes a gray point if the engine is spinning while it is in operation.)

  • Airport signs and ground markings, such as these:

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  • Ground marshaller and wingwalker signals

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    $\begingroup$ All the signs in the world are no match for human stupidity. $\endgroup$ – voretaq7 Jan 12 '15 at 16:33
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    $\begingroup$ Also, most airlines paint danger zones on the pavement that ground crew are required to stay out of. $\endgroup$ – Lnafziger Jan 13 '15 at 4:32
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    $\begingroup$ @Lnafziger is it airlines that paint the pavement or airport that paint the pavement? $\endgroup$ – vasin1987 Sep 10 '15 at 16:04
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    $\begingroup$ @vasin1987 Good question! I believe (but am not sure) that the airlines lease the gates and are responsible for their own painting because they can place equipment wherever they want it, etc. $\endgroup$ – Lnafziger Sep 10 '15 at 19:23
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Spool down times for various engine types allow ramp agents like me to routinely avoid being ingested.i.e when Aircraft is coming up the j-line via direction from ramp agent the rest of the crew maintains a safe distance from the approaching aircraft until appropriate time passes per aircraft at arrival. You can only get ingested once in your life but you can get blasted by jets several times.

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