Starglider From Netherlands, joined Sep 2006, 604 posts, RR: 34 Posted (2 years 11 months 3 weeks 6 days 8 hours ago) and read 3107 times:
Just a thought, focusing on jet airliners. These aircraft are equipped with ice and rain protection systems, used to de-/ anti-ice critical surfaces (mainly leading-edges of wing and tail surfaces) during flight in icing conditions. However, on the ground these systems are de-activated, Some aircraft types (generally those without leading-edge devices) have been equipped with on ground wing leading-edge heating systems in the last decade, using bleed-air to heat the leading-edges at a reduced temperature relative to the airborne systems.
Before flight, the operator has to comply with the clean aircraft concept. No contamination is allowed on any critical aircraft surface. That is why de- and anti-icing procedures are in place and after the treatment, hold-over charts are used, enabling the flight crew to determine time left for a safe take-off. Depending on: starting time of the treatment, temperature, type of ant-icing fluid used, and which precipitation is encountered or expected before take-off.
Fluids used are of environmental concern but now-adays, de-icing spots are usually equipped with drainage systems to keep surplus fluids away from the environment.
On the ground, what would it take to design an aircraft with a de-/ anti-icing system which would heat the entire upper surface of the wing, horizontal en vertical tail, including flight controls, flaps and spoilers? Either "running wet" or "evaporating" systems could be considered. I am aware of arguments raised such as concerns regarding durability of the structures affected by heating and "what ifs," when the system were to fail. But all things considered on the positive side:
1. On the ground it would only be required to raise the surface temperature to 10 deg. C above freezing to prevent any ice from forming. Either by bleed-air or electro-thermal system. Although an electro-thermal system would be more practical.
2. It would mean a lot less anti-icing treatments using fluids which, apart from environmental issues are expensive and take time to perform. It would perhaps still require de-icing the aircraft when frost or precipitation contaminates the surfaces while parked at the gate but with such a system, the anti-icing step would be considerably reduced. A post treatment inspection as currently performed, would still be in place to make sure the aircraft is clean.
3. Less congestion of taxi-ways with aircraft waiting for a de-/ anti-icing treatment on a remote spot.
With the next generation of airliners, like the Boeing 787, having composite wing and tail surfaces, would it be more feasible to introduce such a system?
Fr8Mech From United States of America, joined Sep 2005, 1603 posts, RR: 5 Reply 1, posted (2 years 11 months 3 weeks 6 days 7 hours ago) and read 3099 times:
Weight and complexity come to mind.
Currently, as you pointed out, WAI is inhibited on the ground. The reason for this, is that the temperature of the air is unregulated after it leaves the engine pnuematic system via the PRSOV. This air needs to be hot (upwards of 400F) in order to effectively heat the wing leading edge while in flight. On the ground, these surfaces would quickly overheat. So, we would have to add a cooling medium to the system in order to operate on the ground.
The flight control surfaces, ailerons, elevators, rudders and flaps, normally, will not have any ducts that run to them from the pnuematic system, since they move. So, in order to heat these surfaces, we would need radient heaters imbeded in the surface. Weight, weight and more weight. I suspect that the type of material used in the production of the flight controls would also be changed to something more durable.
CosmicCruiser From United States of America, joined Feb 2005, 1799 posts, RR: 19 Reply 2, posted (2 years 11 months 3 weeks 6 days 7 hours ago) and read 3094 times:
Fr8Mech said it all but to add another facet to this problem...the fuselage needs to be clean as well since any ice or clumps of snow will always find their way into the eng inlet when they break off...hence the clean AIRPLANE concept.
Best idea....bid warm climates in the winter
Troubleshooter From Germany, joined Feb 2005, 419 posts, RR: 5 Reply 4, posted (2 years 11 months 3 weeks 6 days 7 hours ago) and read 3083 times:
Quoting TristarSteve (Reply 3): While true on all aircraft that I work on, The B737 NG has WAI that can be selected on on the ground.
Just want to add that one thermal switch in each wing shuts down the system and closes the wing anti-ice valve if the temperature reaches 125°C. The system resets below this temperature.
Flight152 From United States of America, joined Nov 2000, 3138 posts, RR: 11 Reply 5, posted (2 years 11 months 3 weeks 6 days 6 hours ago) and read 3079 times:
Quoting TristarSteve (Reply 3): The B737 NG has WAI that can be selected on on the ground.
Only for testing the system, then it must be shut off.
Dream as if you'll live forever, live as if you'll die today
TristarSteve From Sweden, joined Nov 2005, 2903 posts, RR: 23 Reply 6, posted (2 years 11 months 3 weeks 6 days 6 hours ago) and read 3066 times:
Quoting Flight152 (Reply 5): Only for testing the system, then it must be shut off.
I assume there must be some operator prefs in here.
Some B737NG ( and later -3/4/500) can select WAI on the ground.
As troubleshooter says there are thermostats that cycle to keep the temp down, but the crews can leave it in. There was a thread on Pprune recently about this, and some Ryanair pilots said they always select it ON after start in icicng conditions.
Seems strange when most aircraft it will NOT come on on the ground.
Starglider From Netherlands, joined Sep 2006, 604 posts, RR: 34 Reply 7, posted (2 years 11 months 3 weeks 6 days 6 hours ago) and read 3065 times:
Quoting CosmicCruiser (Reply 2): Fr8Mech said it all but to add another facet to this problem...the fuselage needs to be clean as well since any ice or clumps of snow will always find their way into the eng inlet when they break off...hence the clean AIRPLANE concept.
Best idea....bid warm climates in the winter
That is why i mentioned the clean aircraft concept in the starting thread. You are correct in pointing out the fuselage as "critical", depending on aircraft configuration, e.g. has a tail engine, like the MD11 or L1011 or at the rear, such as MD-80 or Fokker 100 types, the fuselage will be treated when contaminated with any precipitation. In many other cases the fuselage is de-iced when precipitation has adhered to it above a certain determined limit.
Quoting Fr8Mech (Reply 1): Weight and complexity come to mind.
Quoting Fr8Mech (Reply 1): On the ground, these surfaces would quickly overheat. So, we would have to add a cooling medium to the system in order to operate on the ground.
The flight control surfaces, ailerons, elevators, rudders and flaps, normally, will not have any ducts that run to them from the pnuematic system, since they move. So, in order to heat these surfaces, we would need radient heaters imbeded in the surface. Weight, weight and more weight. I suspect that the type of material used in the production of the flight controls would also be changed to something more durable.
If bleed-air was the chosen medium, i agree with regard to the complexity. Although the Fo70/100 uses reduced heating when on ground wing leading edge heating is selected, relative to WAI in flight. But would a hybrid system do, leaving the WAI as it is now and an electro-thermal system for the large areas and flight controls? A lot of composite research and development done for use in possible SST airframes come to mind.
Quoting TristarSteve (Reply 3): While true on all aircraft that I work on, The B737 NG has WAI that can be selected on on the ground.
Is that system also based on reduced bleed-air pressure/temperatures on the ground like in the F070/100 (if i recall correctly)? For clarity, the system is not to be used for de-icing purposes but is intended to be used in addition to approved de- or anti-icing procedures. This because if used as a de-icer, it could cause run-back ice as the wing is not heated in this day and age.
CosmicCruiser From United States of America, joined Feb 2005, 1799 posts, RR: 19 Reply 9, posted (2 years 11 months 3 weeks 6 days 4 hours ago) and read 3045 times:
I remember on the old 727 you could/must test it on the grd when t/o in icing conditions but there was a time limit for holding the valves open due to overheat risks. On the MD-11 you can select "on" the wing and tail anti-ice switches and have blue value open lights but in reality they're only armed and will open only when the grd sensing senses flight. Of course eng anti-ice works on grd.
HAWK21M From India, joined Jan 2001, 28091 posts, RR: 60 Reply 10, posted (2 years 11 months 3 weeks 5 days 19 hours ago) and read 2990 times:
Quoting TristarSteve (Reply 3): The B737 NG has WAI that can be selected on on the ground.
For the Classics It should be under test only.The Switch too is momentary on the Classics & their is a thermal sw that closes the WTAI Valve in case of high temperatures.However there is no test position on the NGs.
TristarSteve From Sweden, joined Nov 2005, 2903 posts, RR: 23 Reply 11, posted (2 years 11 months 3 weeks 5 days 15 hours ago) and read 2966 times:
B737-3/4/500 works as follows (and I assume NG is the same.)
System operates on ground and in flight. During ground operation thermal switches control the duct temp to 125degC. Actuation of either switch will shut both WAVs. When the switch resets both valves will open again. To provide maximum cooling to the engine bleed air low flow solenoids will energise open the engine precooler valves.
When take off is initiated with antice on the system will shut off automatically to prevent bleed air loss. It can be selected back on when airbourne. Weight off wheels trips the switch on P5 to off.
In the air, the WAI switch opens the valves. Operation of the valves is then not affected by the overheat switches or throttle movement. The precooler will operate normally.
Steve
Starglider From Netherlands, joined Sep 2006, 604 posts, RR: 34 Reply 12, posted (2 years 11 months 3 weeks 5 days ago) and read 2905 times:
If the on ground wing leading edge heating system did not change since introduction more than a decade ago, the Fo70/100 system works as follows:
On the ground, WING leading edge heating is automatically activated when either ENGINE anti-icing system is switched on. The conditions for activating the system are identical to the criteria applicable for engine anti-icing. Provided bleed-air pressure is sufficient (engine bleed-air can be augmented using the APU if needed), the system regulates the temperature of the wing leading edge by opening and closing the wing modulating and shutoff valve. Alerts will be presented in case of a wing leading edge overheat, a control system failure or low temperature due to a system failure or a too low bleed-air supply pressure. The system is inhibited as long as either thrust lever is set above minimum takeoff position, as long as the aircraft is airborne or for approx. 60 seconds after TOGA triggers are activated. Or manually when engine anti-icing is switched off. When landing with engine anti-icing switched on, the system will automatically activate after touchdown with the alerts inhibited.
In the air, wing (and tail) anti-icing systems are activated as required, using the airframe anti-ice switches.
Starglider From Netherlands, joined Sep 2006, 604 posts, RR: 34 Reply 13, posted (2 years 11 months 2 weeks 6 days 5 hours ago) and read 2830 times:
There have been studies considering equipping wind-turbines with anti-icing systems. Effects of rime ice on a 450kW rated power, 27.8 m diameter turbine, operated under both stall-regulated and variable-speed modes have been investigated. Performance losses on the order of 20% were observed in icing conditions for the variable-speed rotor. For the stall-regulated rotor, however, a relatively small rime ice profile yielded significantly larger performance losses. Systems based on electro-thermal heating were investigated. However, it was concluded that for a 100kW turbine, anti-icing by electro-thermal heating requires at least 25% of the maximum power production capacity of the turbine, and the energy required for de-icing by sudden heating far exceeds this capacity.
Considering that the investigation focused on wind-turbines operating in icing conditions while the turbines were generating power, this would be similar to an aircraft wing in flight. Wind-turbines in static conditions, for obvious reasons (not generating power) were not taken in consideration.
Does someone have information about these studied wind-turbine anti-icing systems?
Future aircraft, having composite wing panels, perhaps in combination with self-healing materials now being developed, embedded in their structures, could they find their way in aircraft structures for such purposes as on ground anti-icing?
This may sound far fetched but the new huge wind-turbines that are being installed offshore are being evaluated for such a self-healing application to decrease the failure rate and enhance the lifetime of such large structures.
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