Foggy Windscreen

[pelmet]

Something similar did happen to another crew on one type I used to fly. Their windshield heat failed and I heard they were using credit cards to scrape frost off the cockpit-side window on descent. Perhaps a hairdryer could help for those with electrical outlets.


From TSB....

C-FCRH, a Eurocopter AS 350 B2 operated by Foothills Helicopter Training Academy Ltd. (dba
Exploration Helicopters), was conducting a local flight from Uranium City Airport (CYBE), SK, with
one pilot and 2 passengers. During the walk around, the pilot noticed dew on the windscreen and
wiped the dew off twice prior to starting the helicopter. After starting the helicopter, completing the
checklist, and turning on the demister, the pilot again noticed dew on the windscreen. The engineer
wiped the windscreen from the outside prior to the aircraft departing. C-FCRH departed to the
southwest and climbed above the tree line. After flying approximately half a mile, the pilot was
unable to see outside due to fogging of the front windscreen and side window. The pilot could see
out the passenger-front windscreen. C-FCRH began making a right turn to remain over land and
return to CYBE. After completing the turn, the passenger-front windscreen fogged over. The pilot
used the passenger chin window to see the trees below but there was no reference indicating that
the helicopter was descending. The pilot noticed that the trees appeared to be getting closer and
tried to stop the descent by pulling up on collective. The helicopter settled into the trees, partially
rolling on its left side but was still propped up by the trees. A horn was sounding and the engine
was still running. The pilot shutdown the engine and crawled into the back seat to help unbuckle
the rear passenger. The passengers and the pilot exited out the right-hand door. There were no
injuries to the pilot or passengers. The helicopter sustained substantial damage. The ELT did not
activate. There was no fire. The pilot used a portable radio to call for help. The pilot and
passengers walked to the shoreline and returned to CYBE by boat.

[PilotDAR]

A very similar thing happened to me flying an EC120. It was getting a little foggy inside, and I asked the other pilot to open the windshield defog. Instead of defogging the windshield, it completely fogged it over instantly. What saved the day was that the helicopter as instrument equipped, and I was testing a FLIR camera and display, which I was able to use as a primary reference for "VFR" for 20 minutes while I flew around waiting for the defog to have some effect. Though the fog never did clear, it cleared enough that I could distinguish the freshly paved runway from the grass, and fly an approach down the runway, and hover taxi to the apron. In this helicopter, it is not possible to reach the inside of the windshield while seated. Were it not for being instrument equipped, and having the FLIR, this would have ended much less well. It was a +5C, VMC day in the BC lower mainland.

This photo is after I landed and shut down, nearly 30 minutes after windshield defog was opened!

[PostmasterGeneral]

Do these things not have bleed air for some kind of heat?

[‘Bob’]

Isn’t the big prop on top good enough?

[pelmet]

Isn’t the big prop on top good enough?

Doesn’t do much for the interior.

[PilotDAR]

Do these things not have bleed air for some kind of heat?

I believe so! As It was later explained to me, water can collect somewhere in the system, so the application of windshield defog somehow picks up that water, and makes steam out of it, which fogs when the air hits the cooler windshield. I know that the event I experienced was not the only occasion of this happening in the type....

[5x5]

Just another reason not to ride in an aircraft that has to beat the air into submission in order to fly.