inertial seperators
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They are used to avoid objects getting sucked into the compressor, ie,stones,water,ice, etc. All the Twin Otters that I have flown had the systems made inoperative, as there was no real risk that anything was going to be sucked in due to the height of the engines above the ground, and also we never got any rime ice build up operating around PNG, not below 15000 anyway.
The Bandit had a system that we always used on unsealed, or on sealed airstrips that had fine gravel on them. The seperators where used on landing and take off up to a speed of 40 knots, when at this point we would turn the seporators off to get the required torque.
By memory I think we would lose about 200 torque pounds in the Bandit with the seperators on, and about 2psi torque in the Twotter, and there was also a T5 (EGT) increase, if I can remember correctly. Both systems incorporated a deflector that would drop down in, just aft of the air inlet, this would force any heavy objects, such as stones, or ice to the bottom of the inlet shoot. At the back of the shoot, before the air has to turn 90 degrees and go up, there is a door that comes open when the system is selected on, and the heavy material is ejected overboard. I think both systems on Twotter and Bandit are operated by bleed air.
Hope this helps.
The Bandit had a system that we always used on unsealed, or on sealed airstrips that had fine gravel on them. The seperators where used on landing and take off up to a speed of 40 knots, when at this point we would turn the seporators off to get the required torque.
By memory I think we would lose about 200 torque pounds in the Bandit with the seperators on, and about 2psi torque in the Twotter, and there was also a T5 (EGT) increase, if I can remember correctly. Both systems incorporated a deflector that would drop down in, just aft of the air inlet, this would force any heavy objects, such as stones, or ice to the bottom of the inlet shoot. At the back of the shoot, before the air has to turn 90 degrees and go up, there is a door that comes open when the system is selected on, and the heavy material is ejected overboard. I think both systems on Twotter and Bandit are operated by bleed air.
Hope this helps.
Bell Man,
out of interest what was the benifit of disabling the seperators.
Been a while since I flew either of the two types mentioned, so correct me if I am wrong but there is no penalty if they were not selected On, Open whatever the correct term is??
out of interest what was the benifit of disabling the seperators.
Been a while since I flew either of the two types mentioned, so correct me if I am wrong but there is no penalty if they were not selected On, Open whatever the correct term is??
Props are for boats!
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Bell has it on the bell! Sorry couldnt resist.
They are generally for fod , namely ice in cold regions or at altitude if needed and dirt airstrips in the tropics as well. Depends on what the particular type and POH you have.
They are also known as:
1.Ices Vanes if we are talking King Airs Mr. Beech
and
2.Intake Deflectors if we are talking (De Haviland Canada)
now Bombardier
Renupp the effect of deploying the deflectors reduces intake air , (due the diversion of more air)and therefore reduces Torque output.
I have flown King Airs between FL200 AND FL240 and have had some ice and used them it does reduce the power.
Same on the Otter, the problem with some of the machines in tropics they are permanently disabled ( not correctly and they drop sometimes on there own accord) Youll know because you have to put IN MORE power lever so to speak and therefore fuel in to get the same output, which usually results in a higher ITT or T5.
Regards
Sheep
They are generally for fod , namely ice in cold regions or at altitude if needed and dirt airstrips in the tropics as well. Depends on what the particular type and POH you have.
They are also known as:
1.Ices Vanes if we are talking King Airs Mr. Beech
and
2.Intake Deflectors if we are talking (De Haviland Canada)
now Bombardier
Renupp the effect of deploying the deflectors reduces intake air , (due the diversion of more air)and therefore reduces Torque output.
I have flown King Airs between FL200 AND FL240 and have had some ice and used them it does reduce the power.
Same on the Otter, the problem with some of the machines in tropics they are permanently disabled ( not correctly and they drop sometimes on there own accord) Youll know because you have to put IN MORE power lever so to speak and therefore fuel in to get the same output, which usually results in a higher ITT or T5.
Regards
Sheep
Last edited by Sheep Guts; 21st Dec 2002 at 04:57.
PPRuNe Handmaiden
Shorts call them Ice Vanes too.
Join Date: Jun 2001
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Engine Intake Bypass Doors on the DHC-8
They're supposed to work either manually (electric) or automatically (frangible) if you ingest something like a bird.
However, both the birdstrikes I've had involving them going down the intake have resulted in the doors remaining firmly closed and the only evidence being Kentucky Fried Hawk in the inter-stage pipes and a few feathers stuck in the Bypass Door.
It says a lot for Pratt & Whitneys' robustness.
On another note, some light A/C use them in the cabin ventilation system to keep water out of the air vents when flying through rain.
A very simple inertial seperator is the ventilation system on most cars. The air goes down a vent in the scuttle plate just below the windscreen where there is a pressure difference. The air goes in but the water goes elsewhere.
However, both the birdstrikes I've had involving them going down the intake have resulted in the doors remaining firmly closed and the only evidence being Kentucky Fried Hawk in the inter-stage pipes and a few feathers stuck in the Bypass Door.
It says a lot for Pratt & Whitneys' robustness.
On another note, some light A/C use them in the cabin ventilation system to keep water out of the air vents when flying through rain.
A very simple inertial seperator is the ventilation system on most cars. The air goes down a vent in the scuttle plate just below the windscreen where there is a pressure difference. The air goes in but the water goes elsewhere.
