Pitot/static icing
 

Just been embroiled in a long discussion about the following effects on a KingAir sized aircraft (or smaller pistons). How are people for definitive answers to the following effects?

From 0kts to Lift Off
............................................................ . ASI.................. ALT...................VSI
Pitot Blocked (before moving)
Static Blocked (before moving)
Pitot and Static Blocked (before moving)

Established in a steady unaccelerated climb, then
............................................................ . ASI.................. ALT...................VSI
Pitot Becomes Blocked
Static Becomes Blocked
Pitot and Static Become Blocked

Established in Cruise, then
............................................................ . ASI.................. ALT...................VSI
Pitot Becomes Blocked
Static Becomes Blocked
Pitot and Static Become Blocked


Nosing over and accelerating on descent with the
............................................................ . ASI.................. ALT...................VSI
Pitot Blocked
Static Blocked
Pitot and Static Blocked


Established on descent profile, then
............................................................ . ASI.................. ALT...................VSI
[/B]
Pitot Becomes Blocked
Static Becomes Blocked
Pitot and Static Become Blocked

From 0kts to Lift Off

Pitot Blocked (before moving) 0 IAS / no effect / no effect
Static Blocked (before moving) normal ASI (ignoring any localised static changes) / const altitude / 0 ROC
Pitot and Static Blocked (before moving) 0 ias / const altitude / 0 ROC

Established in a steady unaccelerated climb, then

Pitot Becomes Blocked overead ASI / no effect / no effect
Static Becomes Blocked underread ASI / const altitude / 0 ROC
Pitot and Static Become Blocked stuck IAS / const altitude / 0 ROC

Established in Cruise, then

Pitot Becomes Blocked Stuck IAS / no effect / no effect
Static Becomes Blocked normal read / const alt. / 0 ROC
Pitot and Static Become Blocked stuck IAS / const alt. / 0 ROC


Nosing over and accelerating on descent with the

Pitot Blocked decreasing IAS / no effect / no effect
Static Blocked overread / const alt. / 0 ROC
Pitot and Static Blocked stuck IAS / const alt. / 0 ROC


Established on descent profile, then

Pitot Becomes Blocked decreasing IAS / no effect / no effect
Static Becomes Blocked overread / const. alt / 0 ROC
Pitot and Static Become Blocked stuck IAS / const alt / 0 ROC

Tinnys answers confirmed as correct (not havin a go at you mate, just backing up the reply of a fellow-professional) ;)

Stallie why the sudden worry of blocked pitots in the tropics? Are you newly-endorsed on some raw meat capable of flying in the icing level up there now, or just concerned about them thick pitot-blockin dust-devils around the NT? :D

Oh, he's just concerned about all those icy, snowy runways up there, Slash. You know, a bit of snow flung up into a port or vent, those frequent snow showers to fly through...

Rightly so, too. :D

Thanks boys,

A hypothetical conversation became rather embroiled over a few beers over a couple of the situations above (many are pretty self explanatory obviously).

Your answers above are just what I needed to settle the argument, as I do not have any handy reference texts as 'proof'!

No, not a thing for sub FLs in the tropics of course, although a swarm of locusts might block the odd pitot!

Although as you well know it has caused a few a/c to come to grief. Wasn't there a 727? that crashed due pitot icing in the US? That was the instigator of said conversation.

CS

I've recently done a CPL Aircraft General Knowledge exam and the number of questions on pitot/static blocks in different situations was rather staggering. :eek:

I mention dust devils as I accidentley flew into one once about 55 clicks south of Alice in a 207. Apart from almost throwin me upside down I had a frozen pitot which I guessed was full of NT dirt. Over the fence with the ASI readin rediculous numbers is bloodey disconcerting to look at! Got in ok by opening the side window and keeping a 'feel' on the breeze outside. Floated like hell down RNW 12 which means I think I was 20 odd knots over the mark.

PS yeh I went into it because my head was buried in a friggin porn mag! Searchlight as I recall.

Reading a porn mag whilst flying an aeroplane ! :eek:

No wonder you ended up in a sticky situation. :rolleyes:

You're a bush pilot, right ? :D

The sleaze-mag was thrown at me from the blokes down the back. Told my mate in the right seat (a non-pilot) to keep it straight and level while I just thumb through it a bit. He kept us S & L ok but I was engrossed in one particular page when the twit ran us into a d.devil!

Yep Im still a bushy at heart. ;)

Ima bush pilot....but I like me bush trimmed to a reasonable level (below eyelash/eyeball is about right).

And now let's cut to the quick.........frozen static/pitots.

In fact I experienced one of them..mmmm...once.
Still here to say - NEVER too FAST....NEVER too LOW.

HOT - HIGH & FAST.....beats LOW & SLOW every time!!

The WORST ya EVER gunna get is a "go-round"!! :D

I've had a couple of blocked pitots.

One was a hinged pitot cover that is supposed to unport the opening as IAS increases during take off. It didn't.

The other was my own silly fault with a clear plastic pitot cover with no tag. Ever since I walk right up to the tube... :o

The problems with blocked pitots often are quite obvious and clear cut. Be very wary about the static source which is the root of many evils which often are confusing and anything but clear cut in troubleshooting from the cockpit.

It is a good idea to include a detailed and definite inspection of the static and its surrounding area in the walkaround.

The most obscure example I can recall was a tale of a US military bigbird which had had a mod done well upstream of the static vents. Potential undesirable effects on the PEC were not considered, or considered and discounted ... and were not discovered until during the first takeoff ....