Primarily for general aviation discussion, but other aviation topics are also welcome.
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By PaulB
#1673799
As I said before, I've reported factual inaccuracies in BBC news items and they've been changed.

YMMV
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By KeithM
#1673898
Aside from any legitimate reasons for confidentiality, I think that it’s not unreasonable to suggest that if, indeed, there is any evasiveness involved on anyone’s part, it would likely only serve to increase the attention of the investigators, journalists, the public and, of course, those who have been directly affected, emotionally and financially.
By AFSAG
#1673910
Just playing with some numbers and an online pitot/static simulator

Start at 5000ft and 160 knots, OAT 0c QNH/QNE 1013

Then block the static vent due ice

Effects:
provided neither altitude nor speed change there are no effects

But, descend say 500 ft

Now altimeter shows 5000, but IAS has increased to 180

So slow down to 130 in order to make the IAS 160

Request descent to say 3500

Now indicated altitude is still 5000 but IAS is now 210

So slow down to get IAS right- reduce to 60 and IAS still showing 180
To get IAS to be 160 you need to reduce TAS to less than 0 when the PA46 stalls at ? 60

This is with a complete blockage- partial would be more insidious

We don’t know if the aircraft was hand or autopilot flown- if autopilot even easier to fly into the stall without even realising it

Presume ROV will have looked for alternate static lever position- which would be the solution to the above, but a pilot with degraded performance due to human factors issues around the flight might miss it,

Pitch + power=performance also needs good mental capacity at a time of high stress and startle effect

How easy do static vents ice up in a PA46?
Last edited by AFSAG on Sun Feb 10, 2019 11:02 am, edited 1 time in total.
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By Iceman
#1673913
The Alternate Air lever is a lever that supplies an alternative air source to the engine in the event of induction system icing. An alternate static source will also be available in the aircraft.

Iceman 8)
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By Lockhaven
#1673915
AFSAG wrote:Just playing with some numbers and an online pitot/static simulator

Start at 5000ft and 160 knots, OAT 0c QNH/QNE 1013

Then block the static vent due ice

Effects:
provided neither altitude nor speed change there are no effects

But, descend say 500 ft

Now altimeter shows 5000, but IAS has increased to 180

So slow down to 130 in order to make the IAS 160

Request descent to say 3500

Now indicated altitude is still 5000 but IAS is now 210

So slow down to get IAS right- reduce to 60 and IAS still showing 180
To get IAS to be 160 you need to reduce TAS to less than 0 when the PA46 stalls at ? 60

This is with a complete blockage- partial would be more insidious

We don’t know if the aircraft was hand or autopilot flown- if autopilot even easier to fly into the stall without even realising it

Presume ROV will have looked for alternate static lever position- which would be the solution to the above, but a pilot with degraded performance due to human factors issues around the flight might miss it,

Pitch + power=performance also needs good mental capacity at a time of high stress and startle effect

How easy do static vents ice up in a PA46?


Run the same scenario again but this time block the pitot and see what the results are.

Maybe failed pitot heat, or pitot heat not turned on, or maybe the pitot heat couldn't cope with icing.

If I remember correctly the static ports on the Malibu are on either side of the rear fuselage so unlikely to ice up.






.
Last edited by Lockhaven on Sun Feb 10, 2019 11:15 am, edited 1 time in total.
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By G-BLEW
#1673917
A PA46 observation passed on to me a few years ago by a Piper production test pilot.

…if there's icing in cruise, keep the speed above 140 kts.


I presume the increased AoA below 140 kts allows ice to form beyond the reach of the boots.

That said, although icing is mentioned frequently in relation to this accident, I personally haven't seen an icing forecast for the time/area.

Ian
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By SteveC
#1673918
G-BLEW wrote:A PA46 observation passed on to me a few years ago by a Piper production test pilot.

…if there's icing in cruise, keep the speed above 140 kts.


I presume the increased AoA below 140 kts allows ice to form beyond the reach of the boots.

That said, although icing is mentioned frequently in relation to this accident, I personally haven't seen an icing forecast for the time/area.

Ian


It was posted elsewhere and severe icin was shown.
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By Uptimist
#1673920
Just curious (I have no IR): would it be usual to cross check GPS supplied altitude and ground speed (if available) against that reported by mechanical altimeter/ASI in icing conditions, or would you only think to do that once you were aware of a possible problem (e.g. blocked vent), by which time perhaps it would be too late?
By KeithM
#1673946
Uptimist wrote:Just curious (I have no IR): would it be usual to cross check GPS supplied altitude and ground speed (if available) against that reported by mechanical altimeter/ASI in icing conditions, or would you only think to do that once you were aware of a possible problem (e.g. blocked vent), by which time perhaps it would be too late?


The same thought occurred to me whilst watching a repeat of the documentary about the Air France disaster. (I’m assuming here that such an aircraft would have GPS kit).

I am not a commercial pilot but would be interested to know if fitted GPS is included as part of any troublesheeting procedures or routine in flight checks?

Presumably, had a GPS derived descent trend been noted it could possibly have prevented the incorrect constant pitch up control input apparently applied in the Air France case?
#1673957
Like all of us I’ve run the “what would I have done?” scenarios through my head, which is always easy from the sofa.

AFSAG’s posts about the pitot/static simulator had me re-thinking and once again my head voice was saying “power plus attitude equals performance”, a poor man’s version of the AoA indicator. Which is all well and good I suppose when your wing isn’t covered in ice. Once that happens the AoA limits are unknown and with misleading baro instruments added in you become a test pilot.

I suppose what I’m trying to say is we know the theory and what we should do in those circumstances if we’ve had the training. To be there in such circumstances without the IR training, in bad weather with a (probably) scared passenger is a terrible place to be.
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By G-BLEW
#1673960
Flintstone wrote: power plus attitude equals performance…Which is all well and good I suppose when your wing isn’t covered in ice.


In which case, I guess all you have is power plus attitude and an urgent need to shed ice. If that happens at night, over water, with distractions and accompanied by misleading baro instruments…

I wouldn't fancy my chances

Ian
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By KeithM
#1673969
I also imagine that the altitude at which a problem arises might make a difference as well?

Yes, we would all agree that it’s easy to be wise after the event and whilst sitting on the sofa, but that should, surely, always be a positive thing?
#1673974
Of course Keith. I don't think I was really adding much to all that's been written here, more expressing my view on just how horrible this would have been and Bossman's comment compounds that.

You can train for all sorts of scenarios and talk them over in the hope that should something similar ever happen to one of us we might recall enough to be useful. Anything that reduces the startle effect and our subsequent actions must be A Good Thing.

Although not widely available to light aircraft pilots simulators are great for that. Used wisely they can allow a pilot to leave one after a session of engine fires, failures, electrical faults, system faults etc feeling ten feet tall because he/she dealt with them all. But, and maybe it's just me, when a caption pops up with an amber or red light for real in flight there's a fleeting snippet of time where I hope to hell it's something I/we are going to be able to handle.

Exposure to that 'WTF?' moment by training over and over can lower the stress threshold, free up spare capacity and massively improve one's performance and chances of survival. Sadly, that wasn't the case here where it wasn't a case of not enough training but virtually none at all.
KeithM, Flyin'Dutch', Lockhaven and 1 others liked this
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