Feds and the Caravan/Icing

[ACT700]

US safety board issues warning on Cessna 208 icing
Tue Jan 17, 2006 07:25 PM ET
By John Crawley
WASHINGTON, Jan 17 (Reuters) - U.S. safety investigators issued urgent recommendations late on Tuesday to boost the minimum operating speed of popular Cessna 208 aircraft during light icing and to prohibit their operation when conditions deteriorate beyond that level.
The recommendation to the Federal Aviation Administration from the National Transportation Safety Board follows the review of two fatal crashes last fall in Russia and Canada and covers all models of Cessna's only turboprop.
More than 1,500 single-engine Cessna 208 series planes have been manufactured since 1984. They fly worldwide and are regarded for their versatility, a Cessna spokeswoman said. Their wings are mounted over the fuselage.
Many 208s are used for cargo purposes but some fly passengers and can seat up to 15 people. FedEx Corp. (FDX.N: Quote, Profile, Research) operates the 208 in its large fleet of jets and turboprops, Cessna said.
Cessna, based in Wichita, Kansas, is a unit of Textron Inc. (TXT.N: Quote, Profile, Research)
Icing has been a concern with the 208 series for some time, according to safety records. U.S. safety investigators, the FAA and the manufacturer have sought a mix of inspections, speed requirements and de-icing technology to address the problem, records show.
There have been a dozen icing-related crashes of Cessna 208 models that have killed 33 people in the past 15 years, the safety board said. Nine other icing-related incidents did not result in fatalities.
Even trace amounts of ice on a plane's wing or fuselage can affect aerodynamics and hinder lift, safety experts say.
The FAA said it has taken aggressive action in recent years on Cessna 208 icing problems and continues to work with the manufacturer, which said it was aware of the safety board's urgent recommendation.
The FAA said it expects to take new steps within the coming weeks but did not say whether it would follow the new recommendations.
Last year, the FAA set a minimum speed of 105 knots for operating the Cessna 208 in icing conditions. But the safety board recommended on Tuesday the threshold be increased to 120 knots and the aircraft should not be allowed to operate when conditions deteriorate beyond light icing. The safety board also wants pilots to disengage the autopilot when flying through icy conditions.
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It's been a few years since I've flown the 208, but if I remember correctly, out company min icing speed always was 120kts.

105, I'm pretty sure, would get you in trouble in anything more than light ice.

 

[wrxpilot]

It's been a few years since I've flown the 208, but if I remember correctly, out company min icing speed always was 120kts.

105, I'm pretty sure, would get you in trouble in anything more than light ice.

ACT700,

I've always wondered on these min icing speeds - how do you transition to approach speed if icing conditions are present? Do you just accept the fact that you will be picking up ice for a short time and keep an eye on it during the approach?

 

[MauleSkinner]

I've always wondered on these min icing speeds - how do you transition to approach speed if icing conditions are present? Do you just accept the fact that you will be picking up ice for a short time and keep an eye on it during the approach?

These speeds are designed to keep ice forming only on the protected areas of the airplane, in this case, where the boots are. Slowing below this speed will allow ice to form on the bottom of the wing behind the boot, among other places. I saw a 402 and a Malibu land within an hour of each other that had both tried to climb out of the ice, got slow, and had ice forming to 6 inches behind the front spar on the bottom of the wing.

It's not so much that you'll be picking up ice when you slow down for the approach, it's that you won't be able to get rid of it. Adding flaps will move the impact point forward again somewhat, but if ice has accumulated already, you could end up with some serious aerodynamic issues (tail stall, etc.)

My rule of thumb for the airplanes I fly (I don't fly the Caravan, so I can't say how that would handle) has been to use normal flaps for landing if the airplane has been able to get rid of the ice it's supposed to, and use a reduced flap setting (with substantially more airspeed) if it hasn't.

Fly safe!

David

 

[FN FAL]

ACT700,

I've always wondered on these min icing speeds - how do you transition to approach speed if icing conditions are present?

Why would you need to be transitioning? To let your situational awareness catch up?

When you are in airplane that will slow down in a descent solely because of icing, you don't worry about nothing but transitioning those tires on to the runway...which just happen to be rated for 160 knots.

 

[FN FAL]

These speeds are designed to keep ice forming only on the protected areas of the airplane, in this case, where the boots are.

The only time I have seen ice accrete under or over the boots of a Caravan, was during freezing rain or from run back in clouds during cruise flight. In all other cases, the ice forms on the boots.

The 120 knot icing speed, is the speed we having been using at our company for the past 5 years that I have been working there. In addition, our icing weights have been conservative of factory icing weights, 8,000 max for the 675 hp and 7600 max wt for the 600 hp caravan. It's pilot discretion as to when to use these numbers and there is never a question when the pilot chooses to use these numbers.

 

[MauleSkinner]

The only time I have seen ice accrete under or over the boots of a Caravan, was during freezing rain or from run back in clouds during cruise flight. In all other cases, the ice forms on the boots.

The 120 knot icing speed, is the speed we having been using at our company for the past 5 years that I have been working there.

There ya go! Apparently it works.

 

[ACT700]

fn,
if wxr's profile is any indication, (s)he is a low time pilot, maybe curious about this whole concept of speeds other than one's (s)he's used to.

wxr,

what maule said.

I've been out of the 208 for a few years and cannot recall the icing encounters very well.
All I remember, is going into PQI with max continuous power to keep the thing flying, and no, not full flaps, I think 10*, or 20* max.
I don't ever recall ice building under the wings in the van.
I think, fn correct me if I'm wrong, the icing speed and weight restriction has to do more with the amount of ice (weight) the van builds up, rather than where it builds.

The Metro II would get ice on top of the wing behind the boot quite a bit, but never had a problem flying with it.

The MU2, if you get below (clean) icing speed, which is 180, will build a lot and rather quick under the wing.
So far it hasn't been anything to tighten your turd-cutter over, though.
I forgot how to spell sphincter (?) !

 

[FN FAL]

Company policy is no flaps during icing, hand fly, 120 knots minimum speed, no circling approaches and abide by icing weights.

I think the icing weights and 120 min speed is to make up for loss of lift caused by the ice, not the weight of the ice. With a Caravan, you'll see a loss of 5 knots before you even have enough ice on the boots to actuate them.

They don't want us doing circling approaches with ice on either, so no steep turns. It's pilots discretion...if the circle can be accomplished without turning steep, the pilot can elect to continue with a circling approach, they just don't want you yanking and banking with an impaired airfoil.

CP told us at the last big icing pow wow that the Caravan and the ATR share the same NACA airfoil, so at least we got that going for us.