Strange B200 icing incident

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pelmet
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Strange B200 icing incident

Post by pelmet »

Hard to tell what really happened to cause this....

A13A0128: The Provincial Aerospace Beech 200 aircraft (C-GWUY), operating as Medevac flight SPR810 with 2 pilots, 2 medical personal, 1 passenger and 1 patient on board had departed Sydney en route for Halifax NS. About 30 W of Sydney NS, during the last portion of the climb and initial portion of the cruise, the aircraft encountered icing conditions. The de-ice boots were operating and ice was seen shedding from the wings. After several minutes in cruise the crew requested clearance to 16 000 feet. Almost immediately after starting the climb the airspeed dropped and the aircraft suddenly went nose down, began a shallow turn, and did not respond to elevator inputs. The captain disengaged the autopilot system and increased the nose down pitch to increase the airspeed. The crew declared an emergency. The aircraft levelled off however, the airspeed did not increase and the crew noted a slight vibration. Maximum power was applied and again the crew experienced a similar loss of control. Control was regained and level flight resumed. Total loss of altitude was between 500 and 1000 feet. The crew believed that the T-tail aircraft had encountered a tail plane stall due to ice buildup on the horizontal stabilizer. The crew maintained airspeed above 145 kts to maintain adequate elevator control. The crew confirmed that the de-ice boots were inflating properly by the indicator lights and the pneumatic pressure gauges. After discussing options with ATC the crew elected to descend to 6000 feet and follow the eastern shore of Nova Scotia as the temperature was 7C which would cause the ice to melt. SPR810 landed at Halifax without further incident. Company maintenance confirmed that the de-icing system was operating correctly.
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Navajo Flyer
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Re: Strange B200 icing incident

Post by Navajo Flyer »

Wasn't there a similar icing encounter a few years ago in BC? Between Cranbrook and Kelowna a B200 cooked both engines because of icing and trying to maintain MOCA.
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ahramin
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Re: Strange B200 icing incident

Post by ahramin »

The Cranbrook incident was continued flight in severe icing. Not sure that applies here.

Certainly it's a good reminder to maintain minimum icing speed and hand fly whenever ice is on the airframe.
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Re: Strange B200 icing incident

Post by Captain X »

pelmet wrote:The crew confirmed that the de-ice boots were inflating properly by the indicator lights and the pneumatic pressure gauges.
Indicator lights for the boots??
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frozen solid
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Re: Strange B200 icing incident

Post by frozen solid »

Yeah, some planes have lights that are supposed to tell you when/if the boots are operating on the tail, because unlike the wings you can't see the tail usually. The lights are usually illuminated by a pressure switch, which tells you air is being sent to the boot, unfortunately it doesn't always mean the boot is actually working.
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Re: Strange B200 icing incident

Post by KISS_MY_TCAS »

What Captain X was referring to is the fact that the King Air does not have pneumatic deice indicator lights.
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Re: Strange B200 icing incident

Post by oldtimer »

In the Cranbrook incident, the airplane was an early Beech 200, not a B200. The B200 will preform a lot better.
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ahramin
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Re: Strange B200 icing incident

Post by ahramin »

Oldtimer, are you saying that a B200 would have had a different outcome in the Cranbrook incident?
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Re: Strange B200 icing incident

Post by oldtimer »

I think the Beech 200 was powered by the original PT6-41 engine. Many 200's have been upgraded with either a -42 engine or -42 nickel guide vanes and turbine wheels which either improves performance or makes the engine more durable. A Beech B200 is powered by a PT-6-42 engine. Same rated horsepower but the -42 engine will carry more torque to a higher altitude and with more bleed air available for pressurization, flight at higher altitudes is possible. (In the -42, think power derated to the same 850shp as the original -41)
I knew the pilot involved and I have no idea why he elected to fly the trip at the altitude he did but with a B200, he would have had better altitude performance which may have taken him above the icing and/or allowed him to climb out of icing conditions. The airplane is basically the same. The B200 has some improved systems, pressure differential up from 6.0 psid to 6.5 psid and a 4 blade propeller.
There is so much not said about this incident. I do know both engines were operating and I have taken a lightly loaded 200 to FL330 where it was a good performer and I have also taken a B200 to FL330 where it was a good strong performer.
FYI, it was the same airplane that crashed on a ferry flight a couple of months later when the pilots could not outclimb terrain.
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pdw
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Re: Strange B200 icing incident

Post by pdw »

pelmet wrote:Hard to tell what really happened to cause this....

A13A0128: ....The crew believed that the T-tail aircraft had encountered a tail plane stall due to ice buildup on the horizontal stabilizer. The crew maintained airspeed above 145 kts to maintain adequate elevator control. ...
It's got to be those peculiar icing shapes on account of the large drop icing. Date and time would help to check that out ( a couple of days in December were real nasty for that out there off the ocean).

They might have been right at CofG, otherwise a bit forward can make a "tail plane stall" go total nose-down with a lot of altitude lost very fast. "145 kts" was a fairly rapid minimum speed to just "maintain adequate"
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Re: Strange B200 icing incident

Post by GyvAir »

KISS_MY_TCAS wrote:What Captain X was referring to is the fact that the King Air does not have pneumatic deice indicator lights.
If you replace the word 'indicator' with 'inspection', the report statement makes sense. Sounds like a slip of the tongue to me.
Funny though, in some of the King Air publications.. MM and/or POH, I forget which now.. they reference the surface deice indicator light, but of course when you go looking for it on the panel, it's never there. Or is it on some S/Ns?
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Re: Strange B200 icing incident

Post by Diadem »

pdw wrote:They might have been right at CofG, otherwise a bit forward can make a "tail plane stall" go total nose-down with a lot of altitude lost very fast. "145 kts" was a fairly rapid minimum speed to just "maintain adequate"
What do you mean "right at CofG"? Minimum icing speed in a BE20 is 140, so it makes perfect sense that 145 would have been adequate; considering normal approach speed is 130, Vyse is 121, etc, 145 isn't particularly fast.
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Re: Strange B200 icing incident

Post by frozen solid »

KISS_MY_TCAS wrote:What Captain X was referring to is the fact that the King Air does not have pneumatic deice indicator lights.
Ooops. Never flown one. :oops:
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Re: Strange B200 icing incident

Post by oldtimer »

Just checked my training manuals and the Beech 200, B200, B200C, 300 and 300C do not have surface de-ice indicator annunciators. The Beech 350 has 2 green annunciators, one for wings surface de-ice and one for tail surface de-ice. I do not know about the A200 or the Beech 1300/CATPASS 200. Maybe the newer King Air B200 AND 250 has them because there are always STC's and model upgrades. What they do have is a de-ice pressure gauge that will give a flicker when the boots inflate and deflate plus you can see the wing boots and if you really are anul, you can bend over like a dog screwing a football and look out a passenger window and see the outer portion of the tail, not something most pilots would do.
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Re: Strange B200 icing incident

Post by ahramin »

1300 just has the gauge.
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Re: Strange B200 icing incident

Post by pdw »

Diadem wrote:... 145 would have been adequate; considering normal approach speed is 130, Vyse is 121, etc, 145 isn't particularly fast.
Ooops, I was considering at stall speed you have "adequate elevator control" in clean configuration.

... and here was barely "adequate" at 145 ?

I've heard of a beam of ice (yes like one of those parking beams ... as described by the ramp crew) atop an HS behind the boots and the pilot is recorded as stating "barely noticed it", ... as far as real "strange" goes in icing. Then sometimes it can take not that much of an ice shape at all to make an aircraft behave like it did here. Who knows just how much ice melted off there once reaching the "7C down at 6000ft".

As for the CofG, if balance is Center (or towards aft) the tail structure employs less down-force for maintaining level flight, ie less HS down-lift capability is required. Just saying it then won't be as noticeable if ice-shapes have negated some of the downward lift-capacity on that thinner wing, as in that case a lot less down-lift back there can hold a nose up just fine.
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Re: Strange B200 icing incident

Post by AJV »

pdw wrote: Just saying it then won't be as noticeable if ice-shapes have negated some of the downward lift-capacity on that thinner wing, as in that case a lot less down-lift back there can hold a nose up just fine
I fly these king airs and I have to say, um, what?
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Re: Strange B200 icing incident

Post by AJV »

pdw are you a pilot?
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pdw
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Re: Strange B200 icing incident

Post by pdw »

Yes, except when it comes to tailplane icing and understanding iced tailplane stall there's still some "um, what " too, for sure.

As far as I could tell from researching tailplane aerodynamics is that when ice shapes begin to form across the tail the big risk is when the laminar flow begins to detach on the bottom side of the horizontal stabilizer. When the tail (which is lifting downward always) becomes iced and is lifting the heaviest nose (which can be for a number of reasons that all have something to do with CofG) it has the highest chance of progressing into stall (the flow detachment caused by the ice-shapes that eventually moves back to the elevator hinge-point and can even snap elevator down / yoke forward ... see 'NASA Icing Video'). Here the boots were operating but the lack of elevator effectiveness proved there was still ice back there.

My point was that if loading Center (CofG) is NOT too far forward the flow detachment on the bottom of the HS wing cannot be as severe since its angle of attack (think upside down) is less, is producing less lift, and for that reason was not in risk of snatching the yoke heavily forward to the stops (something like the Nasa Icing Video shows happens on their Otter). Here the boots are working, so there was ice accretion behind them ... maybe more ice on top which is not quite as bad ?
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Re: Strange B200 icing incident

Post by pelmet »

So does the T-tail King Air have an icing problem on the tail that the 100 type does not have?
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Re: Strange B200 icing incident

Post by pdw »

Might have to do with location of the HS, farther up out of the slipstream with the T tail.
pelmet wrote:...during the last portion of the climb and initial portion of the cruise, the aircraft encountered icing conditions. The de-ice boots were operating and ice was seen shedding from the wings.
The initial portion of the cruise, after "ice was seen shedding from the wings", was only several minutes until deciding to climb, but how long had ice been catching on the 'thinner wing' up to that point ? How much earlier ?

When the boots are engaged for visual ice on the wings the tail simply may not have been clearing as well under those particular conditions.
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Re: Strange B200 icing incident

Post by cramer604 »

We pretty much had the same thing happen on our King Air when I worked for West Ex out of Vancouver. We had the fixed wing BCAS contract. When doing daily maintenance ie daily inspections, the t tail was over looked everytime because it is so high up in the air. Long story short. After the incident we got a scissor lift, and manually pressurized the t tail boots and I found 10 pin holes on the left boot and something like 13 on the right boot. Needless to say it was grounded until we could replace the airplane with new boots. So then we brought our other King Air in to the hangar and performed the same check. It had even more holes in its t tail boots! Both airplanes grounded.
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Re: Strange B200 icing incident

Post by GyvAir »

pdw wrote: Here the boots are working, so there was ice accretion behind them ...
I personally wouldn't be very sure that the tail boots were working. There are lots of failure modes that would leave the tail section of the deice system inop while the wing boots continue to function normally. These systems are notorious for working like clockwork in the hangar when under test, but not working when actually needed. Usually when they're being tested, the aircraft isn't cold soaked, so any moisture in the boots and the solenoids or lubricants that well-meaning but ill-informed persons have used on the system aren't going to have the same effect as when everything is frozen solid.
And, as oldtimer says, about the only way to have confirmed that the tail boots were inflating in flight would be to try plastering your face against a passenger window and try to catch a glimpse of the outer foot or two of the boot while the other pilot cycled the system. Not easy at the best of times and after dark on a rainy night, I suspect quite impossible.
Even on systems that have a surface de-ice annunciator, all that tells you is that the solenoid functioned properly and allowed sufficient pressure to build up in the boot manifold during the cycle. If the boot was compromised with stone cuts or static discharge pin holes, there could be enough water inside the boot and tubing that it wouldn't inflate under pressure in freezing temperatures.
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Re: Strange B200 icing incident

Post by pdw »

When the boot rubber is contracting in the cold, "stone cuts or static discharge pinholes" won't be getting any smaller.
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Re: Strange B200 icing incident

Post by swordfish »

In a 1900, when the light illuminates, it confirms that the pressure in the boot has risen, signifying inflation. I didn't fly a 200 with this system...must be a mod.

Several years ago, in a Jetstream, on climb thru 16,000', in clear air (after passing through a shallow layer of icing about 3,000') the tailplane started to vibrate or "shake". Since we were well out of ice, and we're not in rough air, we're thinking control problem, cables, mass balance, loose hinge, couldn't have been flutter as we were on climb. So we leveled off, vibration persists, and we're at out wits end, so popped the boots.

Instant calm. Ice on the tailplane.
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