On Monday my wife and I flew our Jetprop back from London to Perugia (Italy).
From Lyon southeast we were dodging mild looking thunderstorms (the type which peter out at 25,000 ft) with no particular problems.
Ninety miles from our destination we started the descent from FL250, cleared to FL110.
With 10 miles to our next waypoint (VERUN – the start of the normal arrival for Perugia) we entered a moderately dark cloud at about 12,000 ft. After a couple of minutes we starting picking up some ice, but nothing the aircraft could not handle or out of the ordinary for the type of flying we do. The suddenly, at exactly FL110 and -2 C, at the bottom of our cleared descent it became what I would call very heavy – ie freezing rain which was immediately freezing on contact with the aircraft. Ice accumulated at the rate of 1cm plus per minute, in fact almost in seconds. The deice boots were struggling to keep up. I had the presence of mind to quickly monitor the airspeed as the aircraft levelled, and indeed it was slowing quickly, so I increased power to get it back to 145 kts or so. At the same time I got onto the radio with the sector control (Roma) and firstly requested an IMMEDIATE descent below FL110 due heavy icing and the when they refused on the grounds that their “minimum sector radar altitude is FL110” I then told them that if they refused I would declare an emergency and descend to 9,000 ft anyway due extreme icing in order to get below the freezing level. I knew of course that although their minimum radar altitude was FL110, the highest peaks in the Apennines around there were no more than 4 or 5,000 ft high.
As it happened, a few seconds later we suddenly emerged from the other side of the cloud into a broad patch of bright VMC. We were switched to approach and i was able to negotiate a cancellation of IFR and a visual descent and approach, shedding ice rapidly as we went. So all ended fine.
It leads to the question of what I should have done. Obviously I shouldnt have entered the cloud in the first place, and instead looked for longer but safer path to my destination. But having once encountered the heaving icing what should I have done. I know the textbook answer is to execute a 180. But this did not appeal as I knew that it was completely safe if I could get 2,000 ft further down and I didnt like the idea of executing a rapid turn in the turbulence and ice. Had the icing continued a few seconds more I think I would have declared to ATC something like “unable to maintain altitude due extreme icing” and descended anyway.
Any other suggestions?
How was your awareness of the traffic situation around and below you?
Was requesting a lateral deviation from your course and vectors so you don’t enter the ice-laden cloud an option?
I would have asked for an emergency descent to FL090 “due to severe icing”. That would have given you a +4C delta and an assured escape. If they refuse, do it anyway since you know it is terrain-safe. They go home at shift end, but you might be dead…
1cm/minute is probably not “severe” (it is “moderate”) but you need to make an impression 
I’ve had 1cm/minute but the TKS handled it. The problem was I used up most of the tank crossing the Alps doing that, FL160, tops ~FL165, -5C, could not go any higher, and I decided to not do that again in case the TKS pump fails Also 5cm on the wingtips does slow one down a bit.
Buckerfan wrote:
I know the textbook answer is to execute a 180.
From your description, it is not clear to me that a 180 would have helped; you entered the cloud by descent, a 180 staying at FL110 could have stayed in same cloud same icing?
What I do proactively when there is icing forecast on the route and I know it, is that before I get a descent clearance, I ask the controller “due to icing forecast” to NOT level me off between FLXXX and FLYYY, but to keep me FLXXX or higher until he is ready to descend me high speed FLYYY or lower.
The plane I usually fly is… less well de-iced than yours, and on loss of air speed (confirmed by loss of GPS ground speed) I’d be quite quick to escalate to a mayday if the descent clearance does not come very quickly (no time to first try a pan pan). If the GPS ground speed is stable, but the air speed goes down (pitot-static icing), from a calm mind sitting in my armchair I’d say a pan pan, but in situation…
First of all, you did well because the flight was completed safely, you did not lose control at any time, you were aware of the dangers and had a planned out.
I don’t recall if you have radar, but in my experience moderate ice has only happened on yellow/red radar reflectivity
I had a much milder encounter during climb and I acted like you, I should have been more assertive. (Insert link)
The one and only time I had moderate at a similar rate, I immediately took the action I knew would steer us to safety ( in my case a change of course, in your case likely a continued descent if you had good terrain awareness) then advised ATC, in that sequence. ATC did not dare question my decision and instead gave the airliner behind us a heading…
Moderate ice is not something to stay at and has caused landmark accidents to airliners.
BTW, in my book, 1cm/min is heavy and that is what I reported to ATC
Don’t fly into dark clouds = dense clouds = likely TCU or CB. If it does happen, maintain around 0 degree pitch and turb penetration airspeed. If icing is a factor, set a safe, lower ALT and fly in level change mode at a safe airspeed (fast enough!). If power is insufficient to keep that speed, the plane will descend and keep flying. If you have capacity tell ATC “XYZ pan pan pan, unable to maintain FL110, descending due to icing for performance reasons.” If not squaw 7700.
Important is to keep the AoA low and not pitch up trying to maintain an ALT/FL when ice laden.
The critical AoA without ice is ~17° and with ice it can be very low, like only ~3°.
Since the Jetprop offers very good climb rates, and in case of terrain below, an escape up can be considered. In the case described above, I’d have done a 180 if a descent wasn’t possible.
Wasn’t the definition “severe icing” and that means ice accretion rate cannot be coped with?
So if the installation was able to cope with the icing it was moderate icing.
The only other option(s) could have included: request vectors around that cloud or descend as late as possible to not have to stay that long in the middle of the ice.
Other than that it sounds like you did everything right and had a good way out as “plan B”.
Antonio wrote:
I should have been more assertive.
Ultimately, as Antonio, Peter and others commented, my failure was not being assertive enough. This is a lesson I have had to relearn time and time again. I read accident reports where this was the key missing element, a pilot ends up dying because he treats the words of ATC as the words of God.
We have to remind ourselves, ATC is there to help us, but at the end of the day the Pilot in Command can legally do whatever in his/her judgement is needed to ensure the safe conduct of the flight.
To respond to some other comments.
I could have requested a lateral deviation before I entered the clouds, and in fact I had been requesting and using “deviations to avoid” the last hour of the flight. My usual practice is to avoid the top of towering cumulus (ie at about FL250 in the cruise), or in the climb, ABSOLUTELY – using a combination of on board radar and Mark I eyeball. But I have found that flying round Europe in the warmer months you often end up having to deal with the bottom of dying cumulus clouds on the arrival sectors of IFR flights. If you have good terrain clearance below the 0 degree level this has always seemed a reasonable approach. In the case of this flight into Perugia a deviation to avoid cloud could have taken me all the way to coast at Grosetto, around and back, some 150NM spo I had elected to push on into the cloud in the descent.
Antonio asked if i have radar. I do, but in a normal descent at 1200 to 1400 fpm it becomes fairly useless as all you are getting is ground return, no matter how much you scan up.
Anyway, thank you for all the comments. And remember – BE ASSERTIVE with ATC when the situation demands.
