4 ms·

Why didn't the pilots just descend when they encountered a failure with the environmental system?

crooked-v 7y ago
I would presume they did, but that it takes ice a lot longer to melt than to form on an aircraft, especially when considering how cold it can be even at breathable altitudes.
jessaustin 7y ago
The canopy was thickly coated with ice. When you're blind you can't VFR. They couldn't use ice-obstructed instruments either, so a rapid descent would have endangered their plane and other aircraft. They did the right thing, suffering frostbite and cooperating with ground control to preserve life and property.
- ekelsen 7y ago
  I wasn't questioning whether they did the right thing. I wanted to understand why the obvious solution of descending (which is what commercial airliners have done successfully on numerous occasions when losing cabin pressurization) didn't work in this case.
  - rconti 7y ago
    Given Washington's geography, the freezing level on the west side of the mountains would have been far higher than on the east side. They might not have been able to descend below freezing until they crossed over the mountains.
  - jessaustin 7y ago
    Yes that's why I said "a rapid descent would have endangered their plane and other aircraft." I seriously doubt that any commercial airliner, with orders of magnitude more volume than this plane and insulation as well, has ever suffered an internal ice-over like the one described here.
ISL 7y ago
With the loss of visibility, descent to an altitude below the freezing-level may not have been possible. The crew returned to NAS Whidbey, which meant that they had to overfly Washington's Cascade Mountains. The freezing level that day was 7,000 feet or less [1], and some of the mountains are taller than that (many near 7k, a big one reaches 10.5k, and Rainier is 14.4k). It also appears to have been cloudy over the mountains from about noon onward. There is a pretty good chance that they were blind until they were sure they were back in the Puget Sound region. I'll bet they descended as soon as they could. [1] https://www.nwac.us/data-portal/location/stevens-pass/q?field_name=temperature&year=2018&custom_startdate=2018-01-29&custom_enddate=2018-01-29 https://www.nwac.us/data-portal/location/stevens-pass/q?fiel...
jml7c5 7y ago
I am not a pilot nor do I have any familiarity with the workings of aircraft (so please take this as pure speculation until a pilot can come in), but I believe the ventilation comes through high-temperature bleed air. The bleed air is dehumidified, cooled through a heat exchanger, then fed into the cockpit. If the ECS went haywire, one failure mode be to not dehumidify the air, and also to run the heat exchanger at full blast (i.e., the "thermostat" basically broke). EDIT: according to https://www.navy.mil/local/pes/Comprehensive%20Review%20PE.pdf https://www.navy.mil/local/pes/Comprehensive%20Review%20PE.p... , ventilation is provided by mixing high temperature bleed air with cooled, dehumidified bleed air in whatever proportion is needed to keep the cockpit at the correct temperature. So assuming the cooled air is reaches -30C or so, an ECS failure that stopped mixing in any hot air would cause the event described.
daveslash 7y ago
If they could confirm that they were not over a populated area, would ejection be a possibility? The article calls out "both pilot and EWO suffered serious injuries due to frostbite". Did they suffer serious injury to avoid ejecting and in order to save the aircraft, or was ejection not an option?
- dmurray 7y ago
  Ejection risks much more serious injuries. One source [0] gives 92% survival rate and a one-in-three chance of a fractured spine. The survival rate is probably higher in this scenario as the plane isn't actively on fire or too low for a parachute, but if it was me I'd sooner lose a finger or two to frostbite. If the situation is bad enough to risk ejecting I don't think the Navy will ever expect you to preserve the plane. [0] https://www.smh.com.au/education/how-dangerous-is-it-to-eject-from-a-fighter-jet-20120730-239mp.html https://www.smh.com.au/education/how-dangerous-is-it-to-ejec...

I would presume they did, but that it takes ice a lot longer to melt than to form on an aircraft, especially when considering how cold it can be even at breathable altitudes.

jessaustin 7y ago

The canopy was thickly coated with ice. When you're blind you can't VFR. They couldn't use ice-obstructed instruments either, so a rapid descent would have endangered their plane and other aircraft. They did the right thing, suffering frostbite and cooperating with ground control to preserve life and property.

ekelsen 7y ago
I wasn't questioning whether they did the right thing. I wanted to understand why the obvious solution of descending (which is what commercial airliners have done successfully on numerous occasions when losing cabin pressurization) didn't work in this case.
- rconti 7y ago
  Given Washington's geography, the freezing level on the west side of the mountains would have been far higher than on the east side. They might not have been able to descend below freezing until they crossed over the mountains.
- jessaustin 7y ago
  Yes that's why I said "a rapid descent would have endangered their plane and other aircraft." I seriously doubt that any commercial airliner, with orders of magnitude more volume than this plane and insulation as well, has ever suffered an internal ice-over like the one described here.

ISL 7y ago

With the loss of visibility, descent to an altitude below the freezing-level may not have been possible. The crew returned to NAS Whidbey, which meant that they had to overfly Washington's Cascade Mountains. The freezing level that day was 7,000 feet or less [1], and some of the mountains are taller than that (many near 7k, a big one reaches 10.5k, and Rainier is 14.4k). It also appears to have been cloudy over the mountains from about noon onward. There is a pretty good chance that they were blind until they were sure they were back in the Puget Sound region. I'll bet they descended as soon as they could. [1] https://www.nwac.us/data-portal/location/stevens-pass/q?field_name=temperature&year=2018&custom_startdate=2018-01-29&custom_enddate=2018-01-29 https://www.nwac.us/data-portal/location/stevens-pass/q?fiel...

jml7c5 7y ago

I am not a pilot nor do I have any familiarity with the workings of aircraft (so please take this as pure speculation until a pilot can come in), but I believe the ventilation comes through high-temperature bleed air. The bleed air is dehumidified, cooled through a heat exchanger, then fed into the cockpit. If the ECS went haywire, one failure mode be to not dehumidify the air, and also to run the heat exchanger at full blast (i.e., the "thermostat" basically broke). EDIT: according to https://www.navy.mil/local/pes/Comprehensive%20Review%20PE.pdf https://www.navy.mil/local/pes/Comprehensive%20Review%20PE.p... , ventilation is provided by mixing high temperature bleed air with cooled, dehumidified bleed air in whatever proportion is needed to keep the cockpit at the correct temperature. So assuming the cooled air is reaches -30C or so, an ECS failure that stopped mixing in any hot air would cause the event described.

daveslash 7y ago

If they could confirm that they were not over a populated area, would ejection be a possibility? The article calls out "both pilot and EWO suffered serious injuries due to frostbite". Did they suffer serious injury to avoid ejecting and in order to save the aircraft, or was ejection not an option?

dmurray 7y ago
Ejection risks much more serious injuries. One source [0] gives 92% survival rate and a one-in-three chance of a fractured spine. The survival rate is probably higher in this scenario as the plane isn't actively on fire or too low for a parachute, but if it was me I'd sooner lose a finger or two to frostbite. If the situation is bad enough to risk ejecting I don't think the Navy will ever expect you to preserve the plane. [0] https://www.smh.com.au/education/how-dangerous-is-it-to-eject-from-a-fighter-jet-20120730-239mp.html https://www.smh.com.au/education/how-dangerous-is-it-to-ejec...