Instrument Rating
Why do it if it's not fun?
Joined: Jul 2001
Posts: 4,782
Likes: 12
From: Bournemouth
A B737 is most likely going to "crash" (i.e. cause a big mess on the ground) if it has a double engine failure in any conditions.
A light aicraft, whether a single or a twin, can quite easilly be landed in a field in the event of its engine, or all of its engines, failing - as long as you can see the field far enough in advance to be able to set yourself up properly for it. It will not "crash" in the sense that you use the word.
A B737 is much bigger, heavier and faster, and would need a bl00dy great big field to be able to land in such that no one is killed or seriously injured. However, it has systems on board which are sufficiently resilliant to make this an extremely unlikely event - so unlikely that it is considered safe enough to allow the general public to use these aircraft for transport.
If the worst does happen in an airliner, the fact that it is generally much higher than a light aircraft (typically around 10 times as high) means it has many more options as far as where it is going to glide to. Although extremely rare, it's not completely unheard of for an airliner to have a failure of all its engines (e.g. due to fuel mismanagement) and glide to an airfield many miles away. I seem to remember hearing of one case where one of the pilots used to race radio controlled cars when he wasn't working, and knew of a disused airport nearby which was often used by the radio-controlled racers, and he managed to successfully land his airliner there when it ran out of fuel - don't know if it's true or not, but it's a good story! I would imagine - although I don't know for sure - that even in an airliner you would need to have good visual conditions to be able to do this.
FFF
--------------
A light aicraft, whether a single or a twin, can quite easilly be landed in a field in the event of its engine, or all of its engines, failing - as long as you can see the field far enough in advance to be able to set yourself up properly for it. It will not "crash" in the sense that you use the word.
A B737 is much bigger, heavier and faster, and would need a bl00dy great big field to be able to land in such that no one is killed or seriously injured. However, it has systems on board which are sufficiently resilliant to make this an extremely unlikely event - so unlikely that it is considered safe enough to allow the general public to use these aircraft for transport.
If the worst does happen in an airliner, the fact that it is generally much higher than a light aircraft (typically around 10 times as high) means it has many more options as far as where it is going to glide to. Although extremely rare, it's not completely unheard of for an airliner to have a failure of all its engines (e.g. due to fuel mismanagement) and glide to an airfield many miles away. I seem to remember hearing of one case where one of the pilots used to race radio controlled cars when he wasn't working, and knew of a disused airport nearby which was often used by the radio-controlled racers, and he managed to successfully land his airliner there when it ran out of fuel - don't know if it's true or not, but it's a good story! I would imagine - although I don't know for sure - that even in an airliner you would need to have good visual conditions to be able to do this.
FFF
--------------
Thread Starter
Joined: Aug 2003
Posts: 128
Likes: 0
From: Southern Europe
Thanks
Do you really need help with that question?
It was more like a statement than a question.
The question was more about the different in IFR flying for big birds and small birds.
Thanks for all posts, the discussion helped me to sort out my toughts and questions, and it have given me something to think about also.
Joined: Mar 2000
Posts: 1,639
Likes: 0
From: TL487591
IO540 asks:
The operative word is eventually. A fair quantity of rime icing can disappear quite quickly once you leave the source of the ice and get into clear air.
By contrast, even a very modest amount of clear ice will often only finally fall off as you push the aircraft into the heated hangar at the end of the flight. This is just a part of what makes it so dangerous.
2D
Would ice not eventually disappear if you enter VMC conditions even though it is still below 0C, due to sublimation?
The operative word is eventually. A fair quantity of rime icing can disappear quite quickly once you leave the source of the ice and get into clear air.
By contrast, even a very modest amount of clear ice will often only finally fall off as you push the aircraft into the heated hangar at the end of the flight. This is just a part of what makes it so dangerous.
2D
Last edited by 2Donkeys; 26th February 2004 at 19:40.
Joined: May 2002
Posts: 379
Likes: 4
From: Sale
24 August 2001; Air Transat A330-200; near the Azores Islands, Portugal: The aircraft was cruising across the Atlantic at 39,000 feet (11,900 meters) on a flight from Toronto to Lisbon when the right engine lost power. The left engine quit about 13 minutes later. Both engines lost power as a result of fuel starvation. There had been a leak in the fuel system near the right engine, and an open crossfeed valve allowed fuel to be lost from both wing tanks. The leak had been noticed by the crew about an hour prior to the engines shutting down, and the aircraft was already diverting toward Lajes military airfield in the Azores. After the last engine lost power, the crew was able to glide for 20 minutes for about 115 miles (185 km) to Lajes airfield and avert a mid-ocean ditching.
Although the landing gear was damaged during the high speed landing, the crew was able to stop the aircraft on the runway. All 13 crew members and 291 passengers survived, though some occupants were injured during a emergency evacuation. Transport Canada later fined the airline C$250,000 (about US$165,000) for maintenance infractions relating to an improper installation of a hydraulic pump on an engine of the incident aircraft.
Although the landing gear was damaged during the high speed landing, the crew was able to stop the aircraft on the runway. All 13 crew members and 291 passengers survived, though some occupants were injured during a emergency evacuation. Transport Canada later fined the airline C$250,000 (about US$165,000) for maintenance infractions relating to an improper installation of a hydraulic pump on an engine of the incident aircraft.
FIS
Joined: Jun 2003
Posts: 13,787
Likes: 0
From: EuroGA.org
2D
So what could one do if one picked up clear ice on the windscreen, and could not descend below the 0C level due to terrain?
I've picked up ice on the wings and probably elsewhere, say 5-10mm, but never on the front window. Perhaps the window demister and the spray from the TKS prop help a little.
So what could one do if one picked up clear ice on the windscreen, and could not descend below the 0C level due to terrain?
I've picked up ice on the wings and probably elsewhere, say 5-10mm, but never on the front window. Perhaps the window demister and the spray from the TKS prop help a little.
Joined: Aug 2001
Posts: 2,414
Likes: 2
From: Europe
So what could one do if one picked up clear ice on the windscreen
and could not descend below the 0C level due to terrain
I have had a couple of icing encounters but luckily enough not of the clear ice type. Hope to be wiser now and not to repeat the exercise.
FD
Sub Judice Angel Lovegod
Joined: Oct 2002
Posts: 2,460
Likes: 0
From: London
Aircraft which are approved for flight in icing conditions have a way of clearing the windscreen of ice.
There are a number of ways of doing this, but the cheapest is to have a heated plate of glass in front of the pilot's screen.
Timothy
There are a number of ways of doing this, but the cheapest is to have a heated plate of glass in front of the pilot's screen.
Timothy
Joined: Jun 2003
Posts: 13,787
Likes: 0
From: EuroGA.org
I am aware of the various known-ice equipment but my question stands: would clear ice NEVER clear through sublimation?
The point is that one can pick up say 1mm of it while climbing through a 1000ft thick layer, and then spend the next 3 hrs VMC on top, at say -5C.
The only time I ever picked up any (what looked like) clear ice was in marginal icing temperatures and it cleared very quickly on the descent so I could not test this.
I don't fly if 0C is below the MSA, en-route.
The point is that one can pick up say 1mm of it while climbing through a 1000ft thick layer, and then spend the next 3 hrs VMC on top, at say -5C.
The only time I ever picked up any (what looked like) clear ice was in marginal icing temperatures and it cleared very quickly on the descent so I could not test this.
I don't fly if 0C is below the MSA, en-route.
Joined: Sep 2002
Posts: 778
Likes: 0
From: London, UK
On my recent trip round the US we'd have not flown at all on 7 out of the 10 days if we'd not flown when the freezing level was below MSA, because it was generally below zero at ground level. But then it was generally far below zero at cruising levels, which made ice less of a problem.
When encountering rime ice the general advice given was to ask for "4,000' higher" immediately. Around the south-east of the UK this too would be a problem, not experienced when flying IFR in the US.
When encountering rime ice the general advice given was to ask for "4,000' higher" immediately. Around the south-east of the UK this too would be a problem, not experienced when flying IFR in the US.
Sub Judice Angel Lovegod
Joined: Oct 2002
Posts: 2,460
Likes: 0
From: London
IO540
I think that you are labouring the point somewhat. I imagine, given my A level knowledge of physics, that the ice will sublimate eventually in dry air which remains below freezing, but, as 2D says, this has little practical application to flying real aeroplanes.
If you pick up ice there are three practical ways of getting rid of it from unprotected parts of the airframe.
i) Descend to below the freezing level, at which point it comes off remarkably quickly.
ii) Pop out into bright sunshine, which, even if the ambient temperature is a little below freezing can produce enough radiant energy to shift the ice eventually ("eventually" meaning 20 odd minutes, not the many hours that sublimation might take.) You can tell that it is radiant heat rather than sublimation because parts of the airframe in shadow take much longer to clear.
iii) Land and, as 2D said, put it in a warm hangar. Even in the hangar the ice can hang around an amazingly long time (hours rather than minutes) because of lack of airflow.
As this thread is turning into "Icing for Dummies"
it might be worth just elaborating the point that drauk is making about altitude. For icing to appear, you need supercooled water, which is to say water which is below freezing temperature, but still liquid. When this meets the airframe it turns to ice. Small droplets form relatively benign rime ice and large droplet form the dreaded clear ice.
The reason that climbing is often the best solution is that supercooled droplets do not exist below -15C, meaning that if the air is cold enough ice cannot form on the aircraft (though any ice you are carrying will persist, pace IO540.)
Very roughly, -15C will be found 7,000' above freezing level, or, if the surface is -5C, -15C will be 5,000' above the ground.
drauk's rule of thumb will reduce the ambient temperature by 8C, which will almost certainly change conditions enough to reduce or eliminate icing.
Sorry, drauk, don't want to steal your thunder, but you seemed to be assuming knowledge that wasn't self-evident in this thread.
Timothy
I think that you are labouring the point somewhat. I imagine, given my A level knowledge of physics, that the ice will sublimate eventually in dry air which remains below freezing, but, as 2D says, this has little practical application to flying real aeroplanes.
If you pick up ice there are three practical ways of getting rid of it from unprotected parts of the airframe.
i) Descend to below the freezing level, at which point it comes off remarkably quickly.
ii) Pop out into bright sunshine, which, even if the ambient temperature is a little below freezing can produce enough radiant energy to shift the ice eventually ("eventually" meaning 20 odd minutes, not the many hours that sublimation might take.) You can tell that it is radiant heat rather than sublimation because parts of the airframe in shadow take much longer to clear.
iii) Land and, as 2D said, put it in a warm hangar. Even in the hangar the ice can hang around an amazingly long time (hours rather than minutes) because of lack of airflow.
As this thread is turning into "Icing for Dummies"
it might be worth just elaborating the point that drauk is making about altitude. For icing to appear, you need supercooled water, which is to say water which is below freezing temperature, but still liquid. When this meets the airframe it turns to ice. Small droplets form relatively benign rime ice and large droplet form the dreaded clear ice.The reason that climbing is often the best solution is that supercooled droplets do not exist below -15C, meaning that if the air is cold enough ice cannot form on the aircraft (though any ice you are carrying will persist, pace IO540.)
Very roughly, -15C will be found 7,000' above freezing level, or, if the surface is -5C, -15C will be 5,000' above the ground.
drauk's rule of thumb will reduce the ambient temperature by 8C, which will almost certainly change conditions enough to reduce or eliminate icing.
Sorry, drauk, don't want to steal your thunder, but you seemed to be assuming knowledge that wasn't self-evident in this thread.
Timothy
Last edited by Timothy; 28th February 2004 at 21:39.
Joined: Sep 2002
Posts: 778
Likes: 0
From: London, UK
Timothy, you can have my thunder (and clear ice and severe turbulence) any time.
For the record, I'd bet money that IO540 knew that ice won't accumulate when its -15C but most likely some people will have found your more detailed explanation of what I'd said very useful. Hence, no need to apologise.
For the record, I'd bet money that IO540 knew that ice won't accumulate when its -15C but most likely some people will have found your more detailed explanation of what I'd said very useful. Hence, no need to apologise.
Joined: Dec 2001
Posts: 546
Likes: 0
From: europe
My memory of A level physics and chemistry is that the phenomina of sublimation is specific to certain substances, iodine for one, which change their state directly between solid and gaseous. Water has three phases , solid, liquid and vapour(gaseous) and therefore the use of the term sublime does not apply to water/ice.
Joined: Aug 2000
Posts: 3,648
Likes: 2
From: UK
Interesting flying today, with both some low cloud around, and some taller snow showers.
The latter confirmed my previous experience that there's little (in this case, no) icing in clouds from which snow is falling -- they're already glaciated. I don't know enough cloud physics to be sure, and I certainly wouldn't want to bet my life on it, but it sounds plausible that supercooled droplets are not going to form snow.
Does that tally with your experience, Timothy?
The latter confirmed my previous experience that there's little (in this case, no) icing in clouds from which snow is falling -- they're already glaciated. I don't know enough cloud physics to be sure, and I certainly wouldn't want to bet my life on it, but it sounds plausible that supercooled droplets are not going to form snow.
Does that tally with your experience, Timothy?
Joined: Dec 2001
Posts: 546
Likes: 0
From: europe
Timothy
Enter 'triple point of water' in Google, and I think you will agree the term sublimation does not have a relevance at the pressures and temperatures experienced in flight.
www.thefreedictionary.com/sublimate
Item 4 has the definition ref iodine
My memory probably has further to travel in time,so further comment is welcome.
Enter 'triple point of water' in Google, and I think you will agree the term sublimation does not have a relevance at the pressures and temperatures experienced in flight.
www.thefreedictionary.com/sublimate
Item 4 has the definition ref iodine
My memory probably has further to travel in time,so further comment is welcome.
Sub Judice Angel Lovegod
Joined: Oct 2002
Posts: 2,460
Likes: 0
From: London
Bookworm, yes, snow seems quite ok to fly through, both in and below cloud, but it can create some wierd visual illusions, especially if strobes are on.
On the sublimation question, I don't understand Keef's interjection, as I thought I said "sublimate" throughout. (If I didn't I meant to.) However, Keef is quite right that the performance I heard Maxim Vengerov give of the Kreutzer Sonata this evening (on the Kreutzer Stradivarius) was sublime.
And, bluskis, I have been saying all along that ice/vapour sublimation is irrelevant to flight, it was IO540 who thought it might be, I simply (and I think correctly) took issue with you as to whether it exists, which, I still hold, it does.
Hmmm, we seem to have come a long way from whether IR's are worth the candle.
Timothy
On the sublimation question, I don't understand Keef's interjection, as I thought I said "sublimate" throughout. (If I didn't I meant to.) However, Keef is quite right that the performance I heard Maxim Vengerov give of the Kreutzer Sonata this evening (on the Kreutzer Stradivarius) was sublime.
And, bluskis, I have been saying all along that ice/vapour sublimation is irrelevant to flight, it was IO540 who thought it might be, I simply (and I think correctly) took issue with you as to whether it exists, which, I still hold, it does.
Hmmm, we seem to have come a long way from whether IR's are worth the candle.
Timothy
Joined: Aug 2000
Posts: 3,648
Likes: 2
From: UK
On the sublimation question, consider the following cases:
1 A liquid turns (completely) into a vapour at a temperature and pressure associated with the two-state phase equilibrium on a phase diagram. That is usually called boiling.
2 Some liquid turns into a vapour when a dry air stream blows over it at a temperature and pressure associated with the liquid state on a phase diagram. That is usually called evaporation.
3 A solid turns (completely) into a vapour at a temperature and pressure associated with the two-state phase equilibrium on a phase diagram. That is usually called sublimation.
4 Some solid turns into a vapour when a dry air stream blows over it at a temperature and pressure associated with the solid state on a phase diagram. What do we call that?
I don't believe there is a special word for it. Some sources indicate that evaporation is reserved for transitions from the liquid state, though that seems inconsistent with processes of creating thin films of metal and semiconductor in ultra-high vacuum, which is customarily called evaporation.
Sublimation doesn't seem to be reserved for case 3, and I don't see why it shouldn't be used for case 4 too, if you want.
Now I'm no scientific lexicographer, but... no hang on, erm, I am a scientific lexicographer, and my opinion FWIW is that it really doesn't matter whether you say that it sublimes, sublimates or evaporates. The problem for pilots is that it happens painfully slowly!
1 A liquid turns (completely) into a vapour at a temperature and pressure associated with the two-state phase equilibrium on a phase diagram. That is usually called boiling.
2 Some liquid turns into a vapour when a dry air stream blows over it at a temperature and pressure associated with the liquid state on a phase diagram. That is usually called evaporation.
3 A solid turns (completely) into a vapour at a temperature and pressure associated with the two-state phase equilibrium on a phase diagram. That is usually called sublimation.
4 Some solid turns into a vapour when a dry air stream blows over it at a temperature and pressure associated with the solid state on a phase diagram. What do we call that?
I don't believe there is a special word for it. Some sources indicate that evaporation is reserved for transitions from the liquid state, though that seems inconsistent with processes of creating thin films of metal and semiconductor in ultra-high vacuum, which is customarily called evaporation.
Sublimation doesn't seem to be reserved for case 3, and I don't see why it shouldn't be used for case 4 too, if you want.
Now I'm no scientific lexicographer, but... no hang on, erm, I am a scientific lexicographer, and my opinion FWIW is that it really doesn't matter whether you say that it sublimes, sublimates or evaporates. The problem for pilots is that it happens painfully slowly!