I flew on a Beech 1900 this week. During decent we flew through IMC weather and condensation streaked across the pax windows. When we touched down the temps were hovering around freezing so I'm assuming the rubber de-icing boots on the leading edge of the wings were on at some point during decent. I was sitting in the emergency exit on the right side, which is just aft of the leading edge and I watched the boots closely but could not see them inflate and deflate. I thought that is how rubber de-icing boots are supposed to work as I watched one time on an ATR-72 flight and noticed the boots around the air intake on the engine inflate and deflate continuously during flight through IMC weather.
Are some de-ice boots inflated continuously with warm bleed air or is it possible the crew just didn't turn on the de-ice during decent on my particular flight on the 1900?
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Boot De-Ice On Beech 1900
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RE: Boot De-Ice On Beech 1900
With deice boots you are supposed to wait for some ice to accumulate on the wing before activating them for a few reasons. The biggest one is that the boots will stretch if there is nothing on them. I've seen a number of older jets come in with boots sagging. Scary. Another big problem is called bridging. Sometimes the ice will form around the boots if it's freezing fast enough and there is a thin layer that does not completely break.
When you're in an aircraft with propellors, you'll know when there is icing. You'll either hear the ice break off the wings when the boots deploy or you'll hear it sling off the props and hit the fuselage. That usually sounds like the aircraft is being hit with flak. Look at the sides of some of the turbojets flying out there and you'll see the fuselage is thicker near the prop arc for this reason.
When you're in an aircraft with propellors, you'll know when there is icing. You'll either hear the ice break off the wings when the boots deploy or you'll hear it sling off the props and hit the fuselage. That usually sounds like the aircraft is being hit with flak. Look at the sides of some of the turbojets flying out there and you'll see the fuselage is thicker near the prop arc for this reason.
DMI
RE: Boot De-Ice On Beech 1900
The boot system on the 1900 works reasonably well. I usually waited until about 1/2 to 3/4 of an inch of ice, or airspeed decaying below 170 to hit the boots. The props and inlet anti-ice would usually be on by then. There is no mistaking the sound of ice hitting the fuselage. If any ice has accumulated on the boots, it is usually fairly easy to see. You can see the tubes expand and contract. They run spanwise and I believe they are on a 6 second cycle.
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TripleDelta
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RE: Boot De-Ice On Beech 1900
If you left the boots running when there was no ice accumulation, would they cause small disruptions in the airflow over the wing (especially concerning boot elements that are on the wing curve itself and not on the leading edge)? Even if they inflate to a centimeter or so, and on a cyclic basis, wouldn't that disturb the airflow and cause oscillations in lift?
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RE: Boot De-Ice On Beech 1900
Yes. A great game to play with new Beech FO's is to trigger the boots right about the time they are finished trimming the aircraft. The boots cause a small pitching moment which will make it feel like the elevator is still a little out of trim. You have to make sure they are so absorbed in flying the aircraft that they don't notice the annunciators though.
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