Tuesday, January 05, 2010

I respect icing, but it usually doesn't make me sweat in the jet.

This turned out to be a long story, so you are forewarned...

We flew up north to Timmins last night for a passenger pickup and return to Toronto. Kitsch was in New York with the Bravo so I was accompanied on this flight by Pepper, a fellow Captain I borrowed from a friendly competitor, and who has allowed me to call him Pepper for this story, so here we go...

Pepper and I had met years before while flying medevacs and had kept in touch, only to wind up years later flying the same type of aircraft out of the same airport. In fact, the last time I flew with him was a few months ago, in 'his' Citation and I was his f/o. Last night it was 'my' Citation and I was Mr 4-bars, not that it really matters for the purpose of this story.

Checking the weather before the flight, we knew a warm front was over our destination. It's all relative, and a warm front in this case means air that's maybe 5 or 6 Celsius overrunning air that's closer to -15c. Precipitation is usually the result, sometimes making beautiful snowflakes. Unfortunately it's not always a joyous occasion, as unfrozen precipitation from the overrunning warm air mass can fall through the cold air layer and (through *magic*) become supercooled without actually freezing until it hits a solid object. You know what's a solid object? An airplane!

If heavy freezing precipitation hits an aircraft, it can easily overpower the most robust anti-ice and de-ice systems ever built, very rapidly destroying the wings ability to produce lift and clogging all sorts of important air intakes, coating radio antennas and frosting over the windshield. For starters.

As a jet we generally don't spend much time in icing conditions - when we take off we can quickly climb up high enough that it's too cold for ice to form, but upon arrival we generally spend about 10 minutes at a low altitude when approaching and landing at an airport. This is all relevant because Timmins was reporting light freezing drizzle throughout the day. I called ahead and made sure the airport operator would have ground personnel available to de-ice us once we landed, and we got that all coordinated. The runway was constantly being sanded and plowed, and the runway friction index was decent, so that part looked fine too.

Anyway, I guess my point is we were primed to expect messy weather and icing, but it was still predicted to be within the capabilities of the aircraft. The conditions didn't look too bad on paper, and the weather was decent at various alternate airports along the route, so we lit up and headed to Timmins.

The departure was uneventful, and we cruised well above any clouds for an hour while talking about airplanes and playing with the on-board satellite weather. We noted the weather in Timmins had improved from absolute minimums to 3 miles visibility in freezing drizzle, with a ceiling of a thousand feet.

ATC told us the tops of the clouds were around 13,000' and we could expect possible ice in the clouds during the descent. I turned on our anti-ice system to let the various parts warm up before we descended through the clouds. Our hot bits got hot and we punched through the tops of the clouds a few minutes later.

It really didn't take long after that.

Me: "Hmm, we sure are picking up a lot of ice"
Pepper: "Yep. Maybe an inch. I can see it on the wingtip light gates. You wanna blow those boots again?"
Me: "Yep"

We were then descending through about 9000' on the approach to Timmins and the icing started to increase in intensity. All our anti-ice equipment was on, and I was regularly cycling the rubber boots on the wings to knock off ice that was just as rapidly accumulating. No huge deal, and not unsafe - everything is functioning as it should. I told myself this as I watched huge plates of ice fall off the wings every time the boots inflated.

A couple of minutes later, ATC lined us up for the runway and we started our final descent along the ILS glideslope into Timmins. We broke through the bottoms of the clouds about 10 miles from the runway.

Normally that's a good thing, but Pepper and I greeted it with consternation. We could see out the side windows just fine, but the ground visibility revealed that our front windshield was completely covered in ice, as in armour-plated. It was dark and we simply hadn't noticed because we wouldn't have seen anything anyway until the last few minutes of the flight. Our windshield is heated by taking hot air from an engine and blowing it over the outside of the windshield, and it's normally a pretty effective system, but the freezing precipitation we were flying through was really sticky, and it simply overpowered our bleed air heat.

I flipped another switch which started to drench the windshield with isopropyl alcohol, much like windshield washer antifreeze. We have about 20 minutes of fluid, which should be more than enough to eventually get the ice off the windshield, but it's not an instant process. In the past 5 years of flying the jet in Canadian winters, I have never gotten to flip this switch before, so I guess that was cool.

Me: "Okay, let's do a missed approach and maybe hold for a few minutes to see if the alcohol does the trick and we can see."
Pepper: "Okay, I'll let ATC know that we want to go around and hold in the icing while waiting for the icing to disappear"
Me: "If worst comes to worst we can always climb up to altitude and let the ice sublimate."
Pepper: "How much does your plane cost to operate per hour?"
Me: "You were adopted and your cat hates you"

Now before you get all freaked out, I want to make the clear point that we are in *NO* danger at any time during this event - if worst came to worst we'd just fly back to Toronto, where the skies were clear, and during the flight the windshield ice would likely sublimate entirely, but the whole point of this trip was to go to pick someone up and bring them to Toronto, so we didn't want to give up just yet.

We turned off all the airvents in the cockpit, further strengthening airflow to the windshield. I slowed the plane down by 80 knots in the hopes that decreased airflow over the windshield will slow ice accumulation and heat dissipation, and maybe let the windshield alcohol soak in a little better.

We executed a missed approach and told ATC why, and they immediately got very curious and wanted all sorts of details which Pepper happily provided. We didn't climb up very high and were able to stay below the cloud layer, which helped slow the accumulation of ice, but the ice never stopped building. Of course all this time I was cycling the de-ice boots constantly, and the wings were doing okay.

We started to orbit the general area of the airport and waited to see what happened next. What happened next was that I started to be able to make out a faint strip near the bottom of the windshield where the alcohol was soaking in and melting some of the ice. Pepper said the visibility out his side was improving also, so that was cool. We decided to shoot another approach and see if we could see the runway by the time we needed to land, so we flew around and got all lined up with the runway again, about 10 miles back from the threshold.

Pepper: "Runway in sight"
Me: "You lie"
Pepper: "No, really. I can see it out my side"
Me: "I got nuthin'. Could you see enough to land if you had to?"
Pepper: "Cool! Yeah I could!"
Me: "Okay, you have control"

Pepper flew the ILS all the way down to a remarkably smooth landing, especially since we land the airplane from the right seat about once a year, usually during sim training. I was only able to see indistinct blobs out the front of my windshield the entire time, but once we got on the ground I was able to taxi by looking out the side windows.

After we landed, 4 ramp guys came out and started to look at the airplane and point. On the unprotected areas of the airplane there was enough ice to supply the cocktail needs of Keith Richards himself.

Our passengers were already there, so we loaded them up and waited while the de-ice truck blasted hundreds of litres and thousands of dollars worth of pink heated de-ice fluid on our airplane, scrubbing her clean and helping protect her while we taxied to the runway for departure.

We departed less than three minutes after getting hosed down, climbing through the icing layers and into clear air less than four minutes after that. The same warm front that was affecting Timmins was also starting to wreak havoc in the Toronto area, and we could see approaching precipitation. We managed to beat the precipitation in and I was able to actually land the airplane on this leg, so that was fun.

I wasn't even going to write about this, but two things made me:

1. An hour after we landed in Toronto, a departing Boeing 777 reported severe icing on the climbout. The Boeing 777 is a totally badass, huge jetliner and for them to report severe icing gives you some indication of the potency of the weather system.

2. This CADORS report, on an aircraft that arrived in Timmins 1 hour after we did:

Date: 2010-01-04

The Beech A-100 aircraft was on a flight from [origin not reported] to Timmins Airport (CYTS). The flight crew reported difficulty seeing out of the cockpit windshield due it being frozen. The flight crew declared an emergency and ARFF services were called out from the city. The aircraft landed at 0313Z without incident and the ARFF service equipment was released.

That gave me the chills when I read it today - I was browsing the CADORS to see if our airplane was mentioned - if an airplane in Canada overshoots for any reason a CADORs report is normally generated, but it appears we might have gotten lucky, both in the CADORS and in real life.

8 comments:

david said...

Seriously? If I go missed in actual IMC in my Cherokee I'll get a CADORS report? Cool!

My Cherokee is a no-fly in FRDZ, of course, so I've never experienced that magnitude of icing, but I once had the gut-wrenching feeling of being stuck in IMC with moderate mixed icing in December, with the threat from Boston Centre of a 10-15 minute VOR hold before getting my turn to fly an approach into KMSS.

Fortunately, it being a Cherokee, instead of declaring an emergency I was able to cancel IFR, spiral 6,000 ft down through a just-big-enough hole in the clouds, and fly VFR low and slow across flat terrain and the St. Lawrence River to the airport (with my scarf tied around the flap handle to remind me not to touch it on landing).

That kind of stunt probably isn't an option in the bizjet, though I was surprised by how much low-level manoeuvring managed in the Thetford Mines approach described your last posting. I don't think about Citations doing that kind of stuff, at the speeds you have to fly.

Keep up the geeky flying details, please!

Blake said...

I agree with David.. Keep up the geeky flying posts :)

I don't suppose this was your pirep?

UACN10 CYTS 050117
YZ
UA /OV CYTS 210010 /TM 0117 /FL028 /TP C550 /IC LGT MXD

Seems as though you were experiencing more than just "light mixed icing".

Millz said...

Another vote for the geek flying posts. Oh, and a vote for all the rest of the posts too! Love your writing and jealous of your plane! :)

Sulako said...

Yeah, that was Pepper's pirep. If you see the altitude (2,800'), it was when we were on approach into Timmins, in the clear. I think the point Pepper was trying to make was that we were encountering light-moderate icing while flying in the clear, but I think it got lost a little bit in the pirep translation. I dunno, I didn't actually hear Pepper make the pirep and I didn't know we had made one until I read Blake's post. I do know we talked a whole lot about our frozen windshield and the 'hearty' moderate icing we were picking up in cloud, but I didn't see any pireps about that. /shrugs

ScurvyDog said...

Sully, it kinda brings back memories of the winter warm front we got stuck flying through in PAA out of YKZ. If I recall you landed looking out the side window and the IPA didn't work till we were taxing in. The consistency or lack of on the CADORS reporting is sometimes a mystery. I recently had a pitot heat fail while in moderated icing. A/s went to zero and I was IMC with ceilings 300ft above mins. I did the proper thing and reported my failure, ATC gave me priority to land. No report. Then I read other reports where a pilot farts while transmitting on the radio and a 3 page report is written.

Sarah said...

Fascinating post(s) lately, thanks.

David .. I don't want ever to be "stuck in IMC with ice"... yikes! Sounds like an emergency to me, though it sounds like you did exactly the right things.

Captain Dave said...

A cool report, literally. I like the part about slowing down to try to keep the fluid on the windscreen.

Anonymous said...

You are at the top of your game Sulako..cool in a challenging situation and alert to the next move. Though I worry about safety and facing the unexpected, I know that you can handle that little jet-dart and weather and your own beating heart xox mom