Monday, July 7, 2014

Talking Hot! Hot! Hot!

Summer operations are in full effect.

My airline prefers flight crews to utilize PCA (preconditioned air) and GPU (Ground Power Units) while at the gate to reduce fuel consumption. PCA and GPU hoses are connected from the jetbridge to the aircraft. Most of the time the air coming out of the PCA hose is nice and cold and the power coming from the GPU is nice and clean. Most of the time.

There are a few gates that are notoriously shooting out bad air and power. We complain, they "get fixed"...and we complain more.

Last week I arrived about an hour early to the aircraft. The outside temp was 31 degrees Celsius. When I walked in the boarding door I was hit with a wall of hot air. After opening the flight deck door I looked at he environmental screen to see the cabin was 38 degrees Celsius and the flight deck was 39 degrees Celsius. The PCA was attached but not blowing out cool air.

After going through the bare minimum required by my airline for checking the flight deck before starting the APU, I fired it up. Once the APU stabilized I turned on both "packs". The term "packs" are aviation slang for the ACMs...which are Air Cycle Machines....which are more or less air conditioners.

I called operations to have the PCA disconnected as it wasn't helping. The reason the interior was warmer than the exterior was due to a confined metal tube. The flight deck was warmer due to all the avionics, screens and windows.

The cool air felt great. It took a solid 30 minutes to cool the cabin to a tolerable 26 degrees. If I had waited until 35 minutes prior to departure (normal time for arriving at the aircraft) the flight would have been delayed as it would have been too warm for boarding. The cabin must be fairly cool before boarding as loading up 50 warm bodies into a confined space raises the temperature quickly.

Besides warm cabins I also have to consider aircraft performance. Jet engines don't perform as well when it's hot. Takeoff distances are longer, climb rates are slower and even the landing distance must be looked at carefully. Landing distance you ask? Let me explain.

My little RJ operates in and out of mostly smaller airports. Smaller airports have shorter runways. Shorter runways mean more brake usage. More brake usage means hotter brakes. Hot brakes are a no go.

Before each takeoff I verify the brake temperatures are in the safe range. They must be in this range to ensure we can have an aborted takeoff and stop safely as well as making sure they won't catch on fire.

Last week I landed on a runway that was just 6000 feet long. The outside temp was 33 degrees. To avoid overheating the brakes I relied heavily on the thrust reversers to slow the aircraft versus the brakes. On most landings I don't use thrust reverse as the brakes do just fine.

Even with the thrust reversers the brakes got a little too warm. While parked at the gate we had the PCA hoses placed near the brakes to help cool them down.

Summer has just begun.



  1. Thanks, 'Geek.' Hilarious, but then not. I did not realize that your line had max (and probably min) temps for boarding operations and yes, much appreciated. I don't mind some early cold in season, but a parked airplane at ~110F interior is not fun. Ground power, carts or direct connect are viable options before firing up the APU, but... what do you do if there are no ground options and your APU is TU (aka, MEL'd)? Internal temps of >110F are not rare a tube that sits for a while, so what DO you do? No airline wants to cancel any flight, but loading at 110F is not smart. What ARE the real options? Thanks. -C.
    P.S. For the pilots, this situation must be about equal with having to deice and anti-ice a Second Time before leaving some cold winter stations. Again, what ARE your options?

  2. Another hot day and no left pack! That means no air conditioning for the flight deck. More later.


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