I don’t believe any aircraft is certified in severe icing conditions,
Obviously not. No technical invention can surpass nature with absolute certainty. No OEM would claim such a thing, not at last due to liability.
but modern airliners would despatch, in the absence of an obvious immediate threat.
Define immediate threat…
How many airline flights are canceled? Due to weather (directly, not due to capacity)? Due to icing specifically (<1%?)
Am glad Part 121 has clear SOPs stating exactly when flight crew can elect to depart in freezing rain and other no go dispatch conditions. Part 121 have no go weather tables.
All Part 121 operators it is no go to depart in moderate freezing rain. At most hubs the same goes for heavy snow (no holdover table), as there is insufficient time from an inspection to take off (less than five minutes).
En-route not allowed to operate in severe icing – that means extra fuel and re routing round SIGMET areas and airline PIREPs.
USA ATC will not send aircraft into severe icing, for example if reported on take off or approach.
God bless America!
@Snoopy as I already explained to A_A my statement of “No aircraft is certified to fly into severe icing” came from a joint FAA/EASA/DGAC report which I posted on this forum some time ago. The report that is.
I also wrote that if I could find it again I would repost it. And I will do just that.
However, I find it strange that you immediately accept the statement from others. Should I not bother sharing?
gallois wrote:
as I already explained to A_A my statement of “No aircraft is certified to fly into severe icing” came from a joint FAA/EASA/DGAC report which I posted on this forum some time ago. The report that is.
The issue I have is not with the statement itself which is obviously true given the definition of severe icing. The issue I have is with your statement (at least implied) that severe icing is an absolute concept and that forecast severe icing means that no aircraft can fly.
I was not implying anything. Or at least it was not my intention. I was just making a statement of fact on " certification.regs". I assume there is an explanation somewhere of the difference between moderate icing and severe icing. I have always assumed that it would have something to do with the likely speed of ice build up in certain conditions.
This is the DGAC published version of the report I referred to. Personally as wary as i was of icing before I read this I became more so after reading it. It is a bit long I’m afraid.
gallois wrote:
I was not implying anything. Or at least it was not my intention.
I didn’t take the time to find your post when I wrote that. Now I did and you were explicit, sorry. You wrote:
Severe icing is indicated with the severe icing symbol on met reports. […]
So it is not dependent on any particular anti or de icing equipment or.how good it is perceived to be.
This is where we disagree. Certainly the icing symbol on weather charts means something (but what?), but as far as the aircraft goes, severe icing is defined essentially as more ice than the aircraft can handle.
Airborne_Again wrote:
as more ice than the aircraft can handle…
…was there not a time factor added to it?
Oh, yes I looked it up in the above ref and this is what it sais, which is of course aircraft-dependant
Going back to the OP, it seems it is specifically about FIKI SEP’s vs non-FIKI SEP’s. Non-FIKI could be anything from zero ice-protection to fully booted/fully TKS’d but missing one or another certification aspect, I am unsure which non/FIKI configuration the OP is referring to.
I have not personally flown FIKI aircraft so I cannot relate to the potential FIKI complacency the OP refers to. I fly a non-deiced Cessna P210, hence I fly it a lot in the FL’s and my icing strategy is avoidance. I have however tried to learn as much as possible about the type in connection with ice.
1979 Cessna P210 and T210 were the first ever FIKI-approved SEP’s. Interestingly, the non-turbo 210 was not approved at the time. I know TKS provides FIKI approval to the type available as an STC regardless of turbo or not but am unsure if non turbo 210’s later did get FIKI approval.
A lot of research was done at the time on the type to get it approved, and some summary can be seen in a 1970’s SAE paper titled “Qualification of Light Aircraft for Flight in Icing Conditions” report 710394 by Paul Leckman from Cessna. The report is centered on trials with a Cessna T210K and a T337F.
Similar but much deeper and formal analysis as in the RV-8 study quoted in this post, with real ice rather than sandpaper , and more relevant to certified types and, specifically, FIKI-certified types.
Here follow a couple of very interesting relevant extracts from that paper, in the hope of shedding some light along the lines of the OP:
This chart is cross-type and probably global warming has shifted things 2000ft higher:
Then-existing FAR 25 (large aircraft) icing criteria was used throughout since no FAR 23 criteria existed at the time. Where “FAR 25 continuous max icing” is referred or if no other mention, the effect reported is that of approximately one inch of clear ice on the leading edge of the wings and proportionate amounts elsewhere depending on the surface, at MTOW (about 1500lbs useful on this type) . Of course lower weights will improve performance.
Interesting the strut contribution to drag in this table (which explains why TKS Cessna 182, 206 and 208 as well as Kodiaks include the struts)
Effect of protection on different surfaces on max climb rate
Effect of protection on different surfaces on power required in cruise (unreported altitude or perhaps 7000ft as used for other sections)
Bearing in mind this is a 285hp aircraft, 75% would be about 210hp which means without changing power setting your cruise would slow down from 178mph clean to 145mph with full protection on, to 100mph with only prop anti ice, and a stalled condition at 90mph with no protection.
Worth noting how flaps 30 increases stall speed vs lesser flap settings when iced up
