Dash 8 Icing Equipment
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Dash 8 Icing Equipment
Could somebody inform and explain the Icing equipment that the dash 8 has? I can't seem to find alot of material on it
Thanks
Put
Thanks
Put
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Airframe Mode Selector Slow/Fast
Guys,
When would you use SLOW and when would you use FAST mode? According to Q400 FCOM we need to select some kind of DEICING MODE whenever SAT is below 5 C deg.
When would I need to switch from SLOW to FAST?
Any suggestions?
When would you use SLOW and when would you use FAST mode? According to Q400 FCOM we need to select some kind of DEICING MODE whenever SAT is below 5 C deg.
When would I need to switch from SLOW to FAST?
Any suggestions?
Jstflyin,
on all of the DH8-400s I know, there are all of the selections You mentioned available for the deicing boots. There is a 4 position switch that offers the following possibilities:
OFF: the boots are not running, but the governing valves are heated according to a schedule dependent on OAT (they are fed engine bleed air that of course contains atmospheric moisture and consequently might freeze up if they were not heated).
MANUAL: the boots are not running either, but the above mentioned valves are heated permanently. This position is used either when the automatic timer has failed or most often in case one single boot fails to inflate (indicated by the DEICE PRESSURE caution light) - virtually every time I have seen this, the selection of this position has freed up the associated valve and got the system going again.
SLOW: The boots are cycled upon initial selection with the following schedule: the boots are inflated 6 seconds each starting with each outboard wing section, then moving inward across 4 sections per wing (the inner two boots are out of line; the left inboard one is inflated simultaneously with the right 2nd boot and vice versa) and continuing with the tail (first inner elevator, upper rudder and #1 engine inlet, then outer elevator, lower rudder and #2 engine inlet). This is followed by a dwell time of 144 seconds - as the cycle takes 36 seconds to run, a SLOW cycle takes 180 seconds=3 minutes to complete.
FAST: Same as before, but with a dwell time of 24 seconds only. So one FAST cycle takes 1 minute only.
Additionally, there is an 8 position rotary switch (of which oddly 2 are OFF - seems there were no 7 position switches available to DH) that allows to activate the individual boot couples manually, should the timer fail (this is used together with the MANUAL mode on the mode selector). The PNF is required to move the switch to the next position every 6 seconds if needed, thereby effectively using up much of his capacity.
Luckystar,
As to when SLOW or FAST are to be used, does Your OM-B have anything to say about this? Here, SLOW is used on initial detection of ice; FAST is then used on pilots discretion when needed. The only execption is approach and departure - on approach in icing conditions, the boots are on FAST and on departure latest in 1000´ AAL they go on FAST as well. A holding in icing conditions also requires FAST to be selected.
By the way, those spigots on the wipers are not exactly reliable. Often have I seen quite a bit of ice accretion on the wing leading edges while the spigots and also the ice detectors were perfectly clean. Must have something to do with the different radii. A quick peek on the wing seems to be the most efficient way of looking for ice on the -400 just like on the older series.
on all of the DH8-400s I know, there are all of the selections You mentioned available for the deicing boots. There is a 4 position switch that offers the following possibilities:
OFF: the boots are not running, but the governing valves are heated according to a schedule dependent on OAT (they are fed engine bleed air that of course contains atmospheric moisture and consequently might freeze up if they were not heated).
MANUAL: the boots are not running either, but the above mentioned valves are heated permanently. This position is used either when the automatic timer has failed or most often in case one single boot fails to inflate (indicated by the DEICE PRESSURE caution light) - virtually every time I have seen this, the selection of this position has freed up the associated valve and got the system going again.
SLOW: The boots are cycled upon initial selection with the following schedule: the boots are inflated 6 seconds each starting with each outboard wing section, then moving inward across 4 sections per wing (the inner two boots are out of line; the left inboard one is inflated simultaneously with the right 2nd boot and vice versa) and continuing with the tail (first inner elevator, upper rudder and #1 engine inlet, then outer elevator, lower rudder and #2 engine inlet). This is followed by a dwell time of 144 seconds - as the cycle takes 36 seconds to run, a SLOW cycle takes 180 seconds=3 minutes to complete.
FAST: Same as before, but with a dwell time of 24 seconds only. So one FAST cycle takes 1 minute only.
Additionally, there is an 8 position rotary switch (of which oddly 2 are OFF - seems there were no 7 position switches available to DH) that allows to activate the individual boot couples manually, should the timer fail (this is used together with the MANUAL mode on the mode selector). The PNF is required to move the switch to the next position every 6 seconds if needed, thereby effectively using up much of his capacity.
Luckystar,
As to when SLOW or FAST are to be used, does Your OM-B have anything to say about this? Here, SLOW is used on initial detection of ice; FAST is then used on pilots discretion when needed. The only execption is approach and departure - on approach in icing conditions, the boots are on FAST and on departure latest in 1000´ AAL they go on FAST as well. A holding in icing conditions also requires FAST to be selected.
By the way, those spigots on the wipers are not exactly reliable. Often have I seen quite a bit of ice accretion on the wing leading edges while the spigots and also the ice detectors were perfectly clean. Must have something to do with the different radii. A quick peek on the wing seems to be the most efficient way of looking for ice on the -400 just like on the older series.
Last edited by Tu.114; 12th Mar 2012 at 07:44.
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They simply vibrate so when ice starts to collect on the probe it measures a change in the frequency that it had been vibrating.
Reliability is ok (but anyway they got two of them), and they are quite sensitive!
The "ice detected" message comes on in the slightest cloud at times, when there is otherwise no ice visible really.
The "ice detected" message comes on in the slightest cloud at times, when there is otherwise no ice visible really.
Originally Posted by Luckystar77
When would you use SLOW and when would you use FAST mode? According to Q400 FCOM we need to select some kind of DEICING MODE whenever SAT is below 5 C deg.
When would I need to switch from SLOW to FAST?
When would I need to switch from SLOW to FAST?
B. If the manual is silent on the specifics, select SLOW on initial ice detection and go to FAST if the ice continues to build or is not being shed quickly enough.
C. If having selected FAST you are still building more ice and/or performance is deteriorating, leave the icing conditions.
From memory the Dash 8 FCOM advised to turn the prop heats ON when encountering icing conditions but to only select the de-ice boots ON once ice was detected (by the pilot's eyes in the 100/200/300 series.)
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The 300 AFM states: " At 400ft agl on initial detection of ice:Airframe Auto selector - FAST"
It also states that in climb, cruise or descent, on initial detection of ice Airframe Auto selector Fast or Slow depending on rate of accumulation.
For Holding, Approach and Landing in icing conditions Airframe Auto selector Fast.
Lots more in Section 4.7 of the AFM.
It also states that in climb, cruise or descent, on initial detection of ice Airframe Auto selector Fast or Slow depending on rate of accumulation.
For Holding, Approach and Landing in icing conditions Airframe Auto selector Fast.
Lots more in Section 4.7 of the AFM.
Last edited by Gooneyone; 13th Mar 2012 at 14:43. Reason: removal of Smiley
