Light twins and icing conditions
Gizajob
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Light twins and icing conditions
A good friend of mine is currently doing his IR on a twin with no de-icing kit. Yesterday, he flew in conditions which resulted in the aircraft picking up some ice (I don't know how much, but his description suggests light to moderate). MSA was above freezing level and cloud tops were to high to get above sensibly.
When my friend questioned the ice build-up, the instructor said it was OK and they should carry on and that my friend should let him know if he was having any control difficulty
.
I'm quite concerned by this intructor's lack of respect for icing and the method of deciding to get out of it (if they could) - am I showing my lack of experience with non-de-iced light twins or is this instructor a bit of a 'maverick'?
When my friend questioned the ice build-up, the instructor said it was OK and they should carry on and that my friend should let him know if he was having any control difficulty
.I'm quite concerned by this intructor's lack of respect for icing and the method of deciding to get out of it (if they could) - am I showing my lack of experience with non-de-iced light twins or is this instructor a bit of a 'maverick'?
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Well personally I would not fly IFR without de-icing/anti-icing kit.
I would be inclined to agree with you, if the a/c picks up ice and has no de-icing kit I would probably get home, unless the instructor is very experienced and im talking rubbish (very possible
).I would prefer to err on the side of caution with ice.
N
I would be inclined to agree with you, if the a/c picks up ice and has no de-icing kit I would probably get home, unless the instructor is very experienced and im talking rubbish (very possible
).I would prefer to err on the side of caution with ice.N
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Without being a "fly on the wall" it is very difficult to give any form of definitive answer to this. It is however a fact that instructors and newly qualified CPL's have had little or no icing experience even in aircraft that are certified for flight in such conditions thus it is very difficult to criticise this particular instructor as we do not know how much experience he has had. In his favour the freezing level was above the MSA thus if things did turn really pear shaped, he could have descended (or may have been obliged to) and normal services would have been restored before an encounter with the hard stuff would otherwise have occurred. How light was the dusting? Had he penetrated briefly a wisp of cloud below 0 degrees C and picked up a little dusting, or was he holding or conducting an airways sector in the stuff which was building up continuously. If either of these was the case then he had clearly assessed that the ice build up was sufficiently slow that he would not experience trouble and would in any case melt it off when he descended. As more experienced bretherin will know, even with a fully de-iced aircraft, it is best to keep out of it if at all possible. Expanding boots on leading edges are not always successful and ice invariably builds up elsewhere on the airframe increasing weight, impairing performance and slowing the a/c down. I don't know how many times, in this situation I have said "10 more knots off the airspeed and I am descending to get rid of this!"
No - I would not castigate this instructor as some have, but if he was picking up clear ice from supercooled rain and the 0 degree isotherm was below his MSA, then I would heartily agree.
P.P.
No - I would not castigate this instructor as some have, but if he was picking up clear ice from supercooled rain and the 0 degree isotherm was below his MSA, then I would heartily agree.
P.P.
Gizajob
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Thanks for your replies folks - reinforcing my own view I think. The instructor is apparently a 747 captain or FO, so experience should not be a question (though I don't know what his experience of flying relatively low in small aircraft is).
P. Pilcher - MSA was above freezing level so descent was not an attractive option - this is what made it particularly bad for me. They apparently flew an airways route almost permanently in cloud. It sounds like they were picking up rime - sufficient to alarm my friend when he heard chunks of ice hitting the fuselage from the props...
I've pointed out the CRM aspects of this to him too - he was concerned about the build-up but the instructor said it wasn't a problem so they carried on. At the very least, it's teaching an inexperienced IR student potentially bad/ fatal habits. Quite aside from flying other than in accordance with the AFM.
I've advised my friend to ask that instructor (tactfully) more about his decision and view of icing - it may reveal something that he can either learn from or use as his own reason for not flying with that guy again.
P. Pilcher - MSA was above freezing level so descent was not an attractive option - this is what made it particularly bad for me. They apparently flew an airways route almost permanently in cloud. It sounds like they were picking up rime - sufficient to alarm my friend when he heard chunks of ice hitting the fuselage from the props...
I've pointed out the CRM aspects of this to him too - he was concerned about the build-up but the instructor said it wasn't a problem so they carried on. At the very least, it's teaching an inexperienced IR student potentially bad/ fatal habits. Quite aside from flying other than in accordance with the AFM.
I've advised my friend to ask that instructor (tactfully) more about his decision and view of icing - it may reveal something that he can either learn from or use as his own reason for not flying with that guy again.
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I have just today finished my IR, and to be honest I would have been worried if any of my flights would have occured in conditions such as those described here. Having seen how quickly even a little shade of ice can build up, I would always personally side on the side of caution...
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Even with deicing, ice still has to be respected.
I had an stabilator jam on Seneca doing IR training, -10 @10000'.
Aircraft Icing Training - Courses
I had an stabilator jam on Seneca doing IR training, -10 @10000'.
Aircraft Icing Training - Courses
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The instructor is apparently a 747 captain or FO, so experience should not be a question (though I don't know what his experience of flying relatively low in small aircraft is).
No - I would not castigate this instructor as some have, but if he was picking up clear ice from supercooled rain and the 0 degree isotherm was below his MSA, then I would heartily agree.
The example set is a poor one. Anti-ice in a light twin exists for one reason only, and that reason is not to allow it to fly in the ice. It's to get it out of the ice.
I once sat through a ground school for the Twin Commander, in which the chief pilot asked who knew how much ice the TC could handle. None of us had an answer, so he announced with some certainty that the airplane could handle all the ice one could throw at it, and would lose only fifteen knots.
A few days later we were returning from a desert location to a mountain location, and were climbing IFR and IMC below the MEA. We were in an area of rapidly rising terrain, which was forcing a considerable amount of moist air upward. We hit the icing about the same time we were cleared to the MEA. In one minute over an inch of ice built, and we lost 50 knots. The airplane passed through blue line, then approached redline, and was descending with full power, with full heat and boots, and no sign of improvement.
ATC finally kicked us loose because we couldn't make the MEA at that point, were descending, and out of radar contact. We continued to descent until we made ground contact, close to dark, and were able to reduce the descent rate coincident with terrain, until we reached a rural airport. While that was going on, the sound of ice coming off the props and hitting the cutline behind us sounded like 12 gauge shotguns going off continuously.
The next morning we were called into the owner's office and asked what the holes were doing in the side of his airplane. We went out to the fuel pumps where the airplane was chocked, and found what we hadn't seen in the dark; considerable damage done to both sides of the airplane.
A few days later, I heard the same chief pilot tell someone that sure enough, the airplane could take all the ice one could throw at it...and lose just 15 knots.
Just not true. Airplanes ahead of us on the same routing didn't get the ice, and behind us. We pased through an area of significant ice build-up due to orographic lifting. Ice can build quickly beyond the capability to control, and should be given a great deal of respect. It doesn't take a lot of ice before you're flying an entirely different airplane...different performance, different characteristics, different capabilities. It can become adverse.
Ice shouldn't be taken for granted. Anti-ice systems shouldn't be taken for granted. Build up some ice, blow one boot and have the other fail, and now you have an assymetrical airfoil with two different lift capabilities and handling...on different sides of the airplane...and you're now a test pilot.
Especially in a training environment, playing with ice is a very foolish thing to do, or to show to a student. Particularly in a light twin.
Two years ago I had occasion to take an assigment in a light turobjet airpalne that required carrying about 3" of ice all the time, and maneuvering it to the lower performance limits (shaker and buffet) regularly. Several different times I found unforecast, unadvertised adverse handling characteristics in the airplane. This is not desirable. This is not something you want in training, nor in an airplane with limited performance, nor an example or habit to be developed.
The instructor who perpetuates this hazard does no one any favors.
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Good morning!
Of course it is. In addition to "the law" the rules stated in the training manual of the flight training organisation have to be respected, which usually are even more conservative than what "the law" requires. For example, ours require twice the legal minima for ILS approaches (400 ft ceiling instead of 200, 1100m RVR instead of 550). And of course, they state: "no icing conditions".
But reality is not only black or white, as we all know. In our part of the world, avoiding icing conditions at all cost would mean to suspend flight training between Ocotber and April. So the final decision about wether to fly or not to fly will always be based upon the judgement and the experience (and to some extent the courage...) of the instructor. I have learned my lesson many years ago when our Seminole became nearly uncontrollable within less than two minutes due to (unpredicted!) icing - the only time in 30 years of flying when I had serious doubts if I would make it back home in one piece.
So for me, forecast or observed (or even suspected!) icing below MRVA is a strict no-go criterium. But sometimes it can be a bit embarassing to tell the student (who has taken the day off and driven all the way to the airport) "sorry, but we can't fly in these conditions" while some colleagues or competitors go flying nonetheless...
Greetings, Max
isnt it against the law to take an aircraft, which has no anti/de-icing, into known icing conditions?
But reality is not only black or white, as we all know. In our part of the world, avoiding icing conditions at all cost would mean to suspend flight training between Ocotber and April. So the final decision about wether to fly or not to fly will always be based upon the judgement and the experience (and to some extent the courage...) of the instructor. I have learned my lesson many years ago when our Seminole became nearly uncontrollable within less than two minutes due to (unpredicted!) icing - the only time in 30 years of flying when I had serious doubts if I would make it back home in one piece.
So for me, forecast or observed (or even suspected!) icing below MRVA is a strict no-go criterium. But sometimes it can be a bit embarassing to tell the student (who has taken the day off and driven all the way to the airport) "sorry, but we can't fly in these conditions" while some colleagues or competitors go flying nonetheless...
Greetings, Max
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I Have over 2000 hrs in Seneca fives so know them reasonably well. These are certified into light icing. I note the poster reported moderate ice. Was this infact moderate or his interpretation of moderate?
For me icing is a scary thing and that comes from experience of having been dripping in the stuff and getting away with it but through that experience I am much more cautious.
One occasion was flying up to Inverness. There was a line of storms crossing Scotland from West to East.
Moving up from the South I was flying airways on top of a solid overcast so that I could eyeball a way through the line of storms ahead. The solid overcast tops kept increasing in altitude. I was then held At FL110 and entered the clouds with a fairly rapid build up. I selected prop heat on and kept an eye on the buildup. I asked for a further climb and was cleared to FL130.
The climb rate was poor and there was a slight vibration.
On top at FL130 unbeknown to me there are three wires which serve the electrical heating on the props and these had sheared which meant there was no anti ice on the left prop( The shearing of the wires was a known problem and later fixed by a Piper approved mod)
The Seneca has counter rotating props and a very large chunk of ice flew off the left prop. It must have projected forwards as the chunk of ice flew across the nose and hit the right prop.
The right prop hurled the chunk of ice into the side of the nose where it punctured a hole and then flew back into the screen disintegrating into a snow storm. I made it into Inverness where it was disovered that the ice had bent one of the three right prop blades.
The above although a complete fluke is totally true.
Icing is a real danger and something not to mess with especially in a light twin deiced/anti iced or not.
Use the deice/anti ice to get out of it not to cruise in it and if controllers wont let you climb or descend get bossy and explain your situation clearly.
Also beware of days when you know you will carry that ice to the ground Its not quite the threat if you know you can loose a few thousand feet and be in warm air still safely above the MSA.
Pace
For me icing is a scary thing and that comes from experience of having been dripping in the stuff and getting away with it but through that experience I am much more cautious.
One occasion was flying up to Inverness. There was a line of storms crossing Scotland from West to East.
Moving up from the South I was flying airways on top of a solid overcast so that I could eyeball a way through the line of storms ahead. The solid overcast tops kept increasing in altitude. I was then held At FL110 and entered the clouds with a fairly rapid build up. I selected prop heat on and kept an eye on the buildup. I asked for a further climb and was cleared to FL130.
The climb rate was poor and there was a slight vibration.
On top at FL130 unbeknown to me there are three wires which serve the electrical heating on the props and these had sheared which meant there was no anti ice on the left prop( The shearing of the wires was a known problem and later fixed by a Piper approved mod)
The Seneca has counter rotating props and a very large chunk of ice flew off the left prop. It must have projected forwards as the chunk of ice flew across the nose and hit the right prop.
The right prop hurled the chunk of ice into the side of the nose where it punctured a hole and then flew back into the screen disintegrating into a snow storm. I made it into Inverness where it was disovered that the ice had bent one of the three right prop blades.
The above although a complete fluke is totally true.
Icing is a real danger and something not to mess with especially in a light twin deiced/anti iced or not.
Use the deice/anti ice to get out of it not to cruise in it and if controllers wont let you climb or descend get bossy and explain your situation clearly.
Also beware of days when you know you will carry that ice to the ground Its not quite the threat if you know you can loose a few thousand feet and be in warm air still safely above the MSA.
Pace
Last edited by Pace; 30th Oct 2008 at 12:02.
I Have over 2000 hrs in Seneca fives so know them reasonably well. These are certified into light icing. I note the poster reported moderate ice. Was this infact moderate or his interpretation of moderate?
It is implicit in the definition of "light icing" that brief exposure is not a "problem":
The rate of accumulation may create a problem if flight is
prolonged in this environment (over 1 hour). Occasional use of
deicing/anti-icing equipment removes/prevents accumulation. It
does not present a problem if the deicing/anti-icing equipment is
used.
But for "moderate icing"
The rate of accumulation is such that even short encounters
become potentially hazardous and the use of deicing/anti-icing
equipment or flight diversion is necessary.
So what do you do in an aircraft with de-ice that is "certified into light icing"? Does the de-icing suddenly stop working after an hour? If it can cope with the ice by use of the available equipment, is it "light" or "moderate"?
A History and Interpretation of Aircraft Icing Intensity ... has some very interesting perspective.
Last edited by bookworm; 30th Oct 2008 at 19:46.
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Bookworm
It is not just the ability of the boots to kick off ice or the prop heating to keep the props reasonably clear.
Ice will be accumulating all over the airframe not just the leading edges and props.
The airflow will be disrupted and the aircraft will also be carrying more weight.
The props even anti iced will not produce as much thrust.
Even keeping your boots clear you will note a drop off in IAS at cruise speed and a further drop as more ice accumulates on the airframe.
The stall speed will increase so your cruise speed decreases and your stall speed increases coming closer together.
On a light twin or single becuase the initial cruise speed isnt high the stall and cruise will get closer and closer.
So its not just about accumulating light ice and the deicing anti icing being able to cope with it but the continued accumulation on all the services not covered by anti ice or deice over longer periods or greater accumulations.
As the speed decays to maintain altitude the greater angle of attack and increased drag from that.
Also as the airflow descreases so does the friction from the airflow. As the angle of attack changes so does the point of ice accumulation on the lifting surfaces.
At that point I will let someone with greater knowledge of flight dynamics take over especially regarding ice accumulations
Pace
So what do you do in an aircraft with de-ice that is "certified into light icing"? Does the de-icing suddenly stop working after an hour? If it can cope with the ice by use of the available equipment, is it "light" or "moderate"?
Ice will be accumulating all over the airframe not just the leading edges and props.
The airflow will be disrupted and the aircraft will also be carrying more weight.
The props even anti iced will not produce as much thrust.
Even keeping your boots clear you will note a drop off in IAS at cruise speed and a further drop as more ice accumulates on the airframe.
The stall speed will increase so your cruise speed decreases and your stall speed increases coming closer together.
On a light twin or single becuase the initial cruise speed isnt high the stall and cruise will get closer and closer.
So its not just about accumulating light ice and the deicing anti icing being able to cope with it but the continued accumulation on all the services not covered by anti ice or deice over longer periods or greater accumulations.
As the speed decays to maintain altitude the greater angle of attack and increased drag from that.
Also as the airflow descreases so does the friction from the airflow. As the angle of attack changes so does the point of ice accumulation on the lifting surfaces.
At that point I will let someone with greater knowledge of flight dynamics take over especially regarding ice accumulations
Pace
Last edited by Pace; 30th Oct 2008 at 23:43.
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Quote from the very first post......
When my friend questioned the ice build-up, the instructor said it was OK and they should carry on and that my friend should let him know if he was having any control difficulty
.
Its a bit late by then, isnt it?
When my friend questioned the ice build-up, the instructor said it was OK and they should carry on and that my friend should let him know if he was having any control difficulty
.Its a bit late by then, isnt it?
It is not just the ability of the boots to kick off ice or the prop heating to keep the props reasonably clear.
Moderate icing is defined as a level of icing that necessitates de-icing equipment. It really doesn't make sense to have certification of de-icing equipment for "light icing". If the equipment is necessary and can cope with the conditions, the icing is "moderate". If it can't cope with the conditions, the icing is "severe".
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Intensity Aircraft Ice Accumulation
Trace Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. It is not hazardous even though deicing/anti-icing equipment is not used unless encountered for an extended period of time (over 1 hour).
Light The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the dicing/anti-icing equipment is used.
Moderate The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or diversion is necessary.
Severe The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.
Trace Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. It is not hazardous even though deicing/anti-icing equipment is not used unless encountered for an extended period of time (over 1 hour).
Light The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the dicing/anti-icing equipment is used.
Moderate The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or diversion is necessary.
Severe The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.
I believe the below is your description
Moderate icing is defined as a level of icing that necessitates de-icing equipment. It really doesn't make sense to have certification of de-icing equipment for "light icing". If the equipment is necessary and can cope with the conditions, the icing is "moderate". If it can't cope with the conditions, the icing is "severe".
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If that was the case icing reports would Vary. ie moderate to a 777 pilot may be severe to a light twin pilot which obviously is not the case in PIREPs
Severe icing is always icing that exceeds the ability of the airplane to contain or remove the ice accumulation; it's ice beyond the specific airplane's capabilities to handle the ice.
Icing reports do vary; absolutely icing reports vary. This is ALWAYS the case with PIREPS. Moreover, the nature of what's reported is subjective according to the individual experience level of the pilot. What is light to one pilot may be moderate to another, even in the same type aircraft. What is light in one type aircraft may be moderate or severe in another type aircraft.
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Moderate-severe. 0.75. Moderate. 0.625. Light-moderate. 0.5. Light. 0.375. Trace -light. 0.25. Trace. 0.125. No icing. 0. Definition. Severity Index
Icing reports do vary; absolutely icing reports vary. This is ALWAYS the case with PIREPS. Moreover, the nature of what's reported is subjective according to the individual experience level of the pilot. What is light to one pilot may be moderate to another, even in the same type aircraft. What is light in one type aircraft may be moderate or severe in another type aircraft.
Surely the categorisation of icing severity HAS to be based on the rate of accumulation and not the ability of a specific aircraft to deal with ice accumulations? I appreciate a pilot report on icing is subjective as in turbulence reports.
Pace