Friday, December 09, 2011

Emergency retardant drops on take-off

One more point that I feel has to made regarding tanker take-offs, whether they be P-2's or other tankers, is the need to make an emergency retardant salvo. There are many things that can go wrong on take-offs, an engine or hydraulic failure are but two examples. The ability to jettison a load of retardant in the event of an emergency can be crucial to a safe return to base by the tanker. As I understand it, most tanker bases have an area, usually stated by coordinates, where tankers may make emergency salvos of their retardant in the event of an emergency.

Different tankers have different cockpit controls and tank configurations. Many tankers have an emergency drop switch in addition to the normal drop switch. What switch the pilot presses in the event of an emergency on or after take-off may depend on the pilot's knowledge of what happens when the emergency drop switch is pressed. Dropping ten tons of retardant at once leaves the tanker uncontrollable for a few nerve wracking seconds. Something that may not be desirable in an emergency. There might be other options.

For example, when I was writing about retardant drops in the DC-7 T-62 two years ago, Larry Kraus (T-62 pic) told me here that the emergency drop switch on all of Butler's DC-7 tankers (including T-62) is configured to salvo the load at a coverage level of five. If I am correct in understanding how this works, a salvo at a coverage level of five might avoid the sudden pitch-up of the nose.

My friend G told me that he always armed the normal drop switch for a coverage level of four:
The emergency dumps I made were all done through the normal drop switch
on the pilot's yoke.  If you use the normal system, the load goes out at a more even rate. It's a controllable, predictable pitch-up.  At a coverage level four, that only takes about 3 seconds, so it is over in a heartbeat and the airplane climbs like it is homesick for the sky.

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