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Continental TurboProp crash inbound for Buffalo

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Continental TurboProp crash inbound for Buffalo

Old 15th Feb 2009, 22:08
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The automatic deicing system was turned on 12 minutes into the flight and remained on, yet there was "no evidence of severe icing". Wouldn't ice on the leading edges of the wings when the deicing system has been continuously on indicate severe icing, bridging or deicing that isn't working? -- thanx for any insight.
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Old 15th Feb 2009, 22:22
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Hello everyone. I would like to bring up some points of interest that deal with the membrane concept of de-icing on the leading edges of wings.

I also at some later point---want to explore with you---the center of balance of the Q400.

After investigating this balloon concept to deice the wings theres doubt in its design and how it will continue to function as it was intended. In short--here is what I have initially concluded (in part).

This inflatable membrane concept has several drawbacks that may cause it not to function as intended.

One factor to consider---Is there moisture in the plumbing system connecting to the membranes? Is the air inside the plumbing 100% free of moisture? Where does the air come from? Is the air drawn in from the atmosphere--like when its raining? Or is the air special---like a can of compressed air used on computers to clean them?

If theres moisture in the plumbing--the lines or membrane can freeze causing a loss of air pressure to the membranes (the membrane will not expand. (Partially explored)

Another thought is this---Inflating and deflating rubber--or whatever material is used-- changes its elastic properties and therefore the original dimensions of the membrane change with usage.

Electric rubber heating pads are far superior to the balloon concept to deice wings--so why use this balloon concept vs. electric heating pads?
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Old 15th Feb 2009, 22:31
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Could someone who knows more than I do explain how the pilots could have actually seen ice on the wings given they are so far aft of the cockpit?
Thanks
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Old 15th Feb 2009, 22:38
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african

No it wouldn't necessarily indicate severe icing, when the boots are on fast mode there is a dwell time of 24 seconds before the cycle starts again, this is plenty of time for ice to acrete. Yesterday on descent I went into an icing layer, as soon as we hit the cloud we had "Ice Detected" flash at us and there was an instant build up. There was ice visible on the leading edges even after a cycle. The boots were doing their job because it was keeping it off and at a certain level. Each symmectric section of the wing (either side) and V & H stabiliser boots are inflated for 6 seconds in the cycle, so technically each part of the leading edges where there are boots are not inflated for 54 seconds, so bridging is not an issue.

Edited: Regarding seeing the leading edges for ice, from the flightdeck I can see the outboard section of the wings, along with the props and spinner. So it is possible
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Old 15th Feb 2009, 22:47
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Everything that flies is unsafe for economic reasons.

I would not consider the Q400 more unsafe than any other aircraft just because of economic reasons.
It is engineered and therefor bears an accepted risk. From an engineering point of view you have a statistical ditribution for the stress of the unit you are building, as well as for its resilience. The curves will overlap, and this overlapping area will resemble the incidents your working piece will fail.
How much engineering intelligence (=money?!) you invest in pushing your distributions apart on the axis and therefor minimize the size of the overlapping area depends on the severitiy in case of failure.
Pencils are engineered, and break way too often during (my) regular use. It's annoying, but usually not life-threatening, therefor the low resilience is commonly accepted. A nuclear powerplant on the other hand is engineered with alot more resilience, because in case of failure, there are more lifes at stake. Aircraft are somewhere in between, and you bet they are closer to nuclear powerplants than to pencils on the scale.

I am pretty sure safety was not on the list of the airlines that don't operate props during the cold season. During a period of lower traffic, what would you do? Two prop flights or rather one jet instead? Serve each and every unimportant outstation or consolidate your traffic? I mean for two props you need two crews, two airport slots, two times the full package of passenger services, maintainance etc. Serve each and every unimportant outstation or consolidate your traffic? What's the cost of NOT operating a jet vs. a prop for 25% of the year? You tell me.
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Old 15th Feb 2009, 22:54
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Can't help but wonder if, in its desire to be open and transparent and present information in a timely manner, the NTSB is creating a double edged sword.

Good as it is for those who are actually employed in the world of aviation to have early feedback from both the CVR and FDR, it leaves those who know much less with a pool of information to misuse.

Despite requests that information provided during media briefings be used with care, keeping in mind the families of the victims at all times, there seems little evidence that this is happening.

Sensationalist headlines regarding status of autopilot and specifically whether Company rules had been violated suggest that general news reporters who attend the regular NTSB press briefings have neither the ability nor the interest to fully understand the facts before hitting the keyboard or filing their piece to camera.

Sad, if not altogether surprising, to hear that the standard of some reporting has led to the NTSB receiving complaints from some of the families affected by this accident. Appreciate this may just involve the minority of news reporters, but some people just seem incapable of learning. Pleased, at least, that these people donít work in the world of aviation.

Last edited by backseatjock; 15th Feb 2009 at 23:17.
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Old 15th Feb 2009, 23:01
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Well this thread seems to be in a spiral dive as well with a lot of could have should haves.

Some of you need to face up to the facts of life. The aircraft are certified to acceptable standards. There is a variety of means to demonstrate that the aircraft meets these standards. Sure it's nice to have newly advanced designs that appear better on paper (albeit with hidden weaknesses yet to be discovered). But the fact is that the aircraft is made to sell within a market, if you can't price it for the market than it will not exist. So the market has to take something else less viable.

Now we once again face the inevitability of the aircraft having to operate in a variable natural environment (rain, icing, birds etc.) Once again it must meet acceptable standards. But since mother nature has such a great variability, it is necessry that the operation also consider the need to avoid encounters which are outside the certified envelop. Part of this avoidance is minimization of the effects of a possible encounter.

In the case of icing, subjective definitions are carried out regarding the severity of the encounter (over a period of time). This is then combined with expected pilot actions like turning on anti-icing, de-icing "early", hand fly the aircraft when making configuration changes during landing, adjust speed for icing conditions etc. etc.

Regardless of the long time before the NTSB can agree on recomendations at the end of this investigation, it really is up to the industry users to learn and take action now to prevent the next accident.

it ain't going to be to bad mouth the aircraft nor the crew is it.

If the job all falls on the pilot's judgement and it is so subjective that it can not be relied, than maybe the commuter hop should not have been dispatched to begin with.

On the other hand if knowlegeable average pilots can make adjustments based on the lessons learned here, then we all better take heed pretty damn quick and stop crapping in our own house.
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Old 15th Feb 2009, 23:05
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for the sake of argument, let's say the plane was clear of ice

sure it looks like ice was a problem...BUT

why would TWO pilots allow a plane to get 40 knots slow, 60 knots slow if they suspected ice?

was the airspeed indicating system compromised on BOTH the capt and fo/s indicator?

Does this thing have an EFIS that shows airspeed, or seperate airspeed indicators...does it have a standby airspeed indicator?

does this plane have an AOA indiactor.

again, let's say there was no ice...how could two pilots let a plane get that slow? were they leveling off and just forgot to add power?
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Old 15th Feb 2009, 23:14
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protectthehornet

It's far too early to answer your questions on the pilots, and it would be wrong of us because this is just idle speculation.

Regarding the rest, I can't see an issue with 2 heated pitot static ports feeding info to the ADCs, there's too many indications that will appear, firstly if ADC1 or ADC2 was getting false info then we'd get an "IAS MISMATCH" indication. It's pretty inconceivable to say both IAS indicators were reading zero.

Regarding the speed tapes, yes there are 2 speed tapes on the PFDs on the Capt & F/O's side giving a digital readout as well. There is a standby IAS readout on the Standby instrument taking it's reading from the standby pitot source, this is totally independant of the Air Data Computers.

There is no AoA indication in the cockpit, only an average AoA taken from the 2 AoA vanes and fed to the appropriate computers.

D777
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Old 15th Feb 2009, 23:16
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Originally Posted by Security007
Hello everyone. I would like to bring up some points of interest that deal with the membrane concept of de-icing on the leading edges of wings.

I also at some later point---want to explore with you---the center of balance of the Q400.

After investigating this balloon concept to deice the wings theres doubt in its design and how it will continue to function as it was intended. In short--here is what I have initially concluded (in part).

This inflatable membrane concept has several drawbacks that may cause it not to function as intended.

One factor to consider---Is there moisture in the plumbing system connecting to the membranes? Is the air inside the plumbing 100% free of moisture? Where does the air come from? Is the air drawn in from the atmosphere--like when its raining? Or is the air special---like a can of compressed air used on computers to clean them?

If theres moisture in the plumbing--the lines or membrane can freeze causing a loss of air pressure to the membranes (the membrane will not expand. (Partially explored)

Another thought is this---Inflating and deflating rubber--or whatever material is used-- changes its elastic properties and therefore the original dimensions of the membrane change with usage.

Electric rubber heating pads are far superior to the balloon concept to deice wings--so why use this balloon concept vs. electric heating pads?
Some answers of a general nature.

The air used to inflate deicing boots is usually drawn from the engines (upstream of the combustion chamber). It is therefore air from the atmosphere, and thus will have humidity in it. It's also pressurised and hot as a result of being pressurised, so it's unlikely that the air in the tubes will form ice. In any case, the system has to be demonstrated in icing conditions for aircraft certification, so any weaknesses in the design should come out at that point.

Electric deicing is not superior to boots - it has a number of problems of its own, including the power required to get equivalent performance, and the need to generate that power from somewhere.

The most effective system around today is almost certainly bleed air used to heat the surface. But it requires a lot of energy from the engines, and isn't a viable solution for all types (nor is it required for all aircraft in the same way).
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Old 15th Feb 2009, 23:25
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Originally Posted by protectthehornet
sure it looks like ice was a problem...BUT

why would TWO pilots allow a plane to get 40 knots slow, 60 knots slow if they suspected ice?

was the airspeed indicating system compromised on BOTH the capt and fo/s indicator?

Does this thing have an EFIS that shows airspeed, or seperate airspeed indicators...does it have a standby airspeed indicator?

does this plane have an AOA indiactor.

again, let's say there was no ice...how could two pilots let a plane get that slow? were they leveling off and just forgot to add power?
Regarding the airspeeds.

Don't forget that the speeds being quoted by the NTSB are being read off the FDR, which is 99% reading the same speeds as the crew saw. Postulating a failure in the pitot static systems (due to ice or anything else) doesn't fit, because if the system were reading erroneously high, right now the NTSB would also be reading those erroneously high speeds. It would take quite some analysis to work out the "real" speeds, analysis I'd bet they have not done.

I'd say that there's no evidence here of a compromised airspeed system. You'd be suspecting that if the speed were HIGH yet the a/c still seemed to have stalled. Here the reported speeds seem if anything to be a bit low, entirely consistent with some kind of stalling scenario.
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Old 15th Feb 2009, 23:28
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let me rephrase

I don't think TWO pilots would let a plane get that slow...PERHAPS a blocked static source some time during the descent left the airspeed indicating higher than it actually was. perhaps the FDR got a good airspeed indication and the pilots got a bad indication due to only some of the static sources blocked?

I mentioned an earlier AD about static sources and wondered if it had been complied with for this plane
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Old 15th Feb 2009, 23:29
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r.e the AD, I have no idea, but someone posted a few pages ago stating that it had been dealt with.
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Old 15th Feb 2009, 23:32
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replying to :/ Mad (Flt) Scientist--

Do you think or have you ever thought ice could form inside the tubing? Its a fair question not to mention the hot air entering the inflatable membrane ---Using hot air to Inflate and deflate rubber--or whatever material is used-- changes its elastic properties and therefore the original dimensions of the membrane change with usage.?
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Old 15th Feb 2009, 23:34
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doesn't the FDR take its airspeed from a third source, maybe the same as the standby a/s?

One source for captain, another for FO, and a third for FDR/standby airspeed?

I don't know about the Q400, but that is the way other planes have worked.

I'm saying that two pilots wouldn't get that slow, but perhaps they were deceived by the instruments somehow.
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Old 15th Feb 2009, 23:36
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The 100 knots airspeed is about the same as the speed of descent per the radar "1800 feet msl to 1000 feet took five seconds". Could that imply little horizontal motion?
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Old 15th Feb 2009, 23:37
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deano, the AD was complied with for some plane in england...there may have been a few planes off the assembly line that didn't get the AD.
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Old 15th Feb 2009, 23:41
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Security, I hope it was yourself who deleted those two comments and not the mods. I was thinking that if that is the best input you can bring to this discussion you don't have a merit to criticize any posts here. Just saying.
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Old 15th Feb 2009, 23:42
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Originally Posted by protectthehornet
doesn't the FDR take its airspeed from a third source, maybe the same as the standby a/s?

One source for captain, another for FO, and a third for FDR/standby airspeed?

I don't know about the Q400, but that is the way other planes have worked.

I'm saying that two pilots wouldn't get that slow, but perhaps they were deceived by the instruments somehow.
Usually the FDR will read from at least one of the pilot's sources. Often (on newer, higher capacity FDRs) you'll get both pilot and copilot sources.

While you want to know the AS for reconstruction, you also want to know what the crew saw. Having only (for example) standby IAS recorded would make it impossible to know what the crew were actually flying in terms of AS.
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Old 15th Feb 2009, 23:45
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Originally Posted by Security007
replying to :/ Mad (Flt) Scientist--

Do you think or have you ever thought ice could form inside the tubing? Its a fair question not to mention the hot air entering the inflatable membrane ---Using hot air to Inflate and deflate rubber--or whatever material is used-- changes its elastic properties and therefore the original dimensions of the membrane change with usage.?
Yes, ice could form but I think its very unlikely. Based on the fact that the technology of boots is old and well known, so if ice inside the boots were an issue it should be known about by now.

Similar logic for the boots materials - they've been around for ever, if material degradation were an issue it should have come out by now. The boots are in any case subjected to maintenance procedures which should catch that kind of thing.

And of course this was a relatively new a/c so any ageing of the boots should be minimal anyway.
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