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Turbo prop icing

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Turbo prop icing

Old 15th Jan 2019, 09:57
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Turbo prop icing

Hi all,

A question for operators of the atr 72-500/600, dash 8 type. How much approximate extra weight is added do you believe to the “class” of these turboprops when you are iced up with 100% ice on the fuselage?

thank you

downwind.
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Old 15th Jan 2019, 10:28
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Originally Posted by downwind View Post
Hi all,

A question for operators of the atr 72-500/600, dash 8 type. How much approximate extra weight is added do you believe to the “class” of these turboprops when you are iced up with 100% ice on the fuselage?

thank you

downwind.
At a recent meeting in Cologne, it was indicated by all the OEMs that additional weight due to icing is insignificant and is low hundreds of KGs only
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Old 15th Jan 2019, 15:03
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A Q400 is 108ft long and just under 9ft wide. For a simplified (rectangular) fuselage plan area of just under 1000 sq.ft. Call it 100m^2. If you had an inch of solid ice over the whole fuselage, you'd have 2.5m^3 of ice. Ice has a density of just under 1tonne/m^3. So that truly ridiculous amount of ice would weight 2.5 tonnes.If you took a more reasonable thickness of ice, a more reasonable assumption of where it would adhere and of the real fuselage area, you'd be down in the hundreds of kg.

More importantly, managing to accumulate such a ridiculous amount of ice and not have the wings contaminated is practically impossible - you'd have to sit in freezing rain for hours, and no anti-icing fluid can protect the wings for that long in similar conditions. if you look at some typical HOT values and some assumed precip rates, you'll find 1/4" or less of ice is more what you might see.
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Old 15th Jan 2019, 22:58
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Had nearly one inch of ice on the Q400 (over the Alps), but didn't notice much performance loss. Few knots of airspeed. But the Q400 is a performance monster.
We had an ATR72 flying ahead, and they were crying for their lives, reporting extreme icing.
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Old 15th Jan 2019, 23:52
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IIRC our Performance Tool adds 50kg to the entered landing weight when icing conditions exist (Q400).
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Old 16th Jan 2019, 10:11
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Ice forms basically at the stagnation points in the airflow. For the fuselage, that would be the nose, a part of the windshield and cockpit roof. The length of the fuselage will not ice up. The wing typically will have arond 6 x 6cm lengthwise and a few cm's cordwise into the airflow (IIRC the Fokker 50 was certified to 6cm ice build up. Correct me if I'm wrong). My rusty calculator says that's about 80 kg in total for a F50 type of aircraft.
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Old 16th Jan 2019, 10:24
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Originally Posted by Mad (Flt) Scientist View Post
A Q400 is 108ft long and just under 9ft wide. For a simplified (rectangular) fuselage plan area of just under 1000 sq.ft. Call it 100m^2. If you had an inch of solid ice over the whole fuselage, you'd have 2.5m^3 of ice. Ice has a density of just under 1tonne/m^3. So that truly ridiculous amount of ice would weight 2.5 tonnes.If you took a more reasonable thickness of ice, a more reasonable assumption of where it would adhere and of the real fuselage area, you'd be down in the hundreds of kg.

More importantly, managing to accumulate such a ridiculous amount of ice and not have the wings contaminated is practically impossible - you'd have to sit in freezing rain for hours, and no anti-icing fluid can protect the wings for that long in similar conditions. if you look at some typical HOT values and some assumed precip rates, you'll find 1/4" or less of ice is more what you might see.
To Add
The basis of the icing regulations assumes continuous icing within appendix "C"

Thus no limitation on time, But you would be extremely unlikely to find ridiculous icing conditions (outside appendic "C") in continuous flight

Even without anti-ice fluid, de-ice devices etc. The insulation effects of the ice on the aircraft surfaces (adherence) coupled with in-flight windage would produce self shedding before dead weight became a problem (unlike naval vessels
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Old 16th Jan 2019, 19:02
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Just to clarify

my calculation was for ice build up on ground (parked at gate, say) and is even more ridiculous compared to inflight cases, of course.
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Old 16th Jan 2019, 19:18
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The loss of lift and or control due to ice accumulation on the wings and tailplane will have a far bigger impact before the total weight ever becomes an issue.

It doesn't take significant amounts of ice to significantly reduce lift.
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Old 18th Jan 2019, 06:52
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The FAA has traditionally published a diagram illustrating an effect of added weight as opposed to the loss of lift. This is nonsense. We have known for decades that the added weight is inconsequential...how much weight have you lost through the fuel burned while you are trying to figure out how much weight the ice has added? The only guy who needs to worry about the weight of accumulated ice is a Zeppelin captain. The loss of lift...and the aerodynamic effects on handling...are by far the more serious effects.
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Old 23rd Jan 2019, 22:47
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I can't remember ice sticking to the fuselage being a concern during >2000 hrs of Alpine Dash 8 ops. There's a bit on the nose and a bit on unprotected parts, but I can't recall any ice accumulating around the outside of the fuselage once you're airborne. I'd prefer to be in a Dash 8-400 rather than an ATR when severe icing hits, can't recall a Dash 8 crashing due to icing.
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Old 24th Jan 2019, 01:10
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Originally Posted by Alpine Flyer View Post
....I'd prefer to be in a Dash 8-400 rather than an ATR when severe icing hits, can't recall a Dash 8 crashing due to icing.
Think the Colgan Ft 3407 accident was at least partly icing related. https://en.wikipedia.org/wiki/Colgan_Air_Flight_3407
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Old 28th Jan 2019, 15:28
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There were no aerodynamic icing effects documented during the Colgan investigation. Colgan was related to icing for two reasons: first, the incorrect reference speed was bugged; it should have been 20 knots higher based on the icing reference switch being selected in conjunction with the operattion of the ice protection system. Second, it is possible that the crew incorrectly perceived the shaker and pusher as an ice contaminated tailplane stall.

But actual ice accretion did not have a role. Alpine Flyer is correct. There have been no Dash 8 accidents due to inflight icing (they respond to inadequate ground deicing, particularly on the upper stabilizer surface, about as well as any airplane...which is to say very poorly). The ATR continues to have difficulties.
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