Rapid Decompression

Hypoxia Training

Early in May, a colleague and I flew to Renton (KRNT) in order to experience the FAA’s portable reduced oxygen training enclosure (PROTE). This chamber is capable of producing hypoxic environments at ground level by altering the fraction of ambient oxygen. This avoids some of the risks associated with pressurized altitude chamber training. The purpose of the chamber is to learn how you will react when experiencing hypoxia and to learn some of the signs associated with hypoxia. The chamber let us experience what it would be like at 27,000’ without supplemental oxygen for five minutes. 

The Flight

We had been watching the weather for a week leading up to the flight and the extended forecasts would alternate back and forth between VFR, MVFR, IFR. Making the flight under IFR conditions wasn’t the issue, but there was a cold air system coming and the freezing levels were forecast to be at 6000’ which is the typical north bound altitude assigned between Portland and Olympia.

On the day of the flight the conditions enroute were reported as VFR with rain showers along the route, so we expected we’d have to deviate around and under areas of lower clouds and rain. We departed KSLE VFR and encountered our first area of rain and low visibility near KHIO, but we were easily able to deviate around the spots of weather and as we approached KSPB there was some precipitation and spotty MVFR conditions ahead. As we neared Kelso (KKLS) the ceilings started to drop and the visibility was decreasing from VFR to MVFR. After a short time of being in low visibility we decided that we needed an IFR clearance in order continue the flight.

While I looked up the ATC frequency for getting a clearance, the pilot flying made a 180 degree turn back to the VFR conditions that we had previously come from while I negotiated an IFR clearance to KRNT with ATC. Since we didn’t have an IFR flight plan filed in the ATC system it some back and forth between the controller to get all the relevant details of the requested clearance, like aircraft type, equipment (/G, /A, etc.), desired route (in our case direct OLM and then KRNT. But once the controller established radar contact with our aircraft he asked us to assume our own terrain clearance until reaching 4000’ before proceeding on course to OLM. For the remainder of the flight he flew the airplane while I handled communication duties with ATC.

Our assigned altitude was 6000’ (remember earlier I mentioned the freezing levels were 6000’)? As we settled in at altitude we were closely monitoring the outside air temperature and watching to make sure that any visible water droplets were moving across the airplane structure and not becoming stationary (freezing). Sure enough, after a short time at 6000’ ice started to form on the wing strut and the leading edge of the wing. Though it was very light ice accumulation, we immediately reported the ice to ATC and requested a lower altitude. We were assigned a new altitude of 5000’ and after descending, the OAT increased to +2 degrees C and the water on the airplane surfaces was moving again.

Once reaching OLM we were switched to Seattle approach and began receiving vectors to the north west of Seattle in preparation for the GPS 16Z approach at KRNT. Overall the flight from KSLE to KRNT took about an hour and a half and about one hour of that was in instrument meteorological conditions (IMC).

GPS 16Z

Landing 16

Hypoxia Training

The chamber holds six people and before each group went in, we were briefed as to what to expect and how to operate our pulse oximeter and demand flow oxygen mask. We were given a clip board with some check boxes that we were supposed mark when we experienced symptoms of hypoxia and some sample math problems to work while in the chamber.  Once in the chamber, the instructor would ask random questions, like “if you burned 10 gallons an hour how many gallons you would use…”. He would pick on individuals that appeared to be out of it do to hypoxia. In fact, a few participants’ heads went limp and the instructor had to put their mask on them. The point of the training wasn’t to see how long you could go without oxygen, but to demonstrate to yourself what your hypoxic limits were and the symptoms that you experience when at high altitudes. As for me, I made it about 2 ½ minutes before feeling too dizzy and nauseous to continue, so I donned the oxygen mask and recovered.  my colleague went the full five minutes without putting on the oxygen mask.

  

The Return Flight

After the training, it was time for lunch before flying back to KSLE so we took the opportunity to fly to one of my favorite dining spots, Mukilteo Coffee Roasters on Whidbey Island, which is adjacent to W10. W10 is located on the southern end of Whidbey Island and is a 20-minute flight from KRNT. The airport is surrounded by trees and has a 2500’ runway, and the café is a short walk up a path from the runway. After lunch we headed for home and were able to make the entire return flight in VFR conditions.