GVII - Aft Equipment Hot

Updated: 2021-08-15

A G600 pilot I know recently had an “Aft Equipment Hot” CAS message, fortunately at a low altitude during approach to landing. His experience poses an excellent thought experiment to help prepare you should this ever happen to you.

- Setting up for the approach they got an “Aft Equipment Hot” red CAS message.

- They immediately shut off the left ENG BLEED AIR switch while referring to the 3A-01-10 AFM procedure.

- The procedure says "APU BLEED AIR - OFF," it already was. Then “Affected Engine — Attempt to Identify,” by all indications it was indeed the left engine. Then “ECS Pack (Affected Engine) — Off” and “Isolation Valve — Closed," they did that. They also turned off the Wing Anti-ice. They did not try the other bleed switch because they were so near to landing.

- After they landed, taxied in, and shut down, one of the pilots felt the aft bulkhead wall from the cabin and noticed it was very hot. They shut down the aircraft completely and gave it to maintenance.

- Upon opening the aft equipment door, a lot of insulation fell out. As it turns out, a coupling inside the aft equipment compartment inboard of the bleed air duct from the right engine had separated. Shutting the right ENG BLEED AIR would have been the next step in the procedure had they not been so close to landing.

- The heat, even for the brief five to ten minutes of this incident, was enough to partially melt some of the wiring insulation in the aft equipment compartment.

From the incident pilot: It might not be a bad idea to treat an “Aft Equipment Hot” message with immediately turning both bleeds off and descending as quickly as possible if needed for pressurization.

I remember from my days flying Air Force GIIIs we would turn both bleeds off and allow the cabin altitude to climb while waiting for the warning to extinguish and negotiating an immediate descent. While waiting we would examine all available engine instruments (about all we had back then) to determine which engine was producing the leak. Once the message extinguished we would turn on the bleed for the other engine and see what happened. If the message came back we would turn off that bleed, let the message extinguish again, and turn on the other bleed.

Of course all this is “off script” and is offered for your consideration.