Icing encounter - your thoughts

blueskyMD

blueskyMD

Pre-takeoff checklist
Joined
Mar 26, 2015
Messages
352
Location
Allentown PA
Display Name
Display name:
Bigfoot297
I just finished the flight and safely landed at KAXQ. Forecast supposed to be broken 2500 with light snow showers and possibility of trace icing. At 8000 I was mostly above the clouds but about 60 miles out to destination I started getting into clouds. Temps were -14 d C. I kept checking wings with flash light and there was just trace amount on leading edges. All was fine until I felt change in engine noise with very slight amount of airframe vibration. Few minutes after that air speed started dropping from 140 IAS to 120 and very quickly went to 80 and then slowly went to 0. Aspen came up with 2 big X es on both screens. Pushed the throttle up and mixture advanced . Pitot heat was on since the engine start. Disconnected auto pilot and switched to alternate static source. But the changed engine noise remained ( almost felt like engine is not producing enough power ) . Also changed to alternate induction air. The airplane was flying fine with " 0 " indicated airspeed. I descended to 4 K ft and started to see ground lights and clouds cleared up After few nervous minutes airspeed became alive and Aspen came back. Rest of the flight was uneventful .
Question is why pitot tube failed despite of being on all the time ( I checked it prior to departure )
And any thought about the changed in engine hum and vibration of airframe ?
 
Dunno what was going on with Pitot icing but have a couple observations.

Looking at the ruc sounding for PIT you were at the top of the icing at 8,000 ft. 10,000 ft would have put you in dry air.

Mixture advanced at 8,000 ft may well degrade power output depending on how rich you pushed it.

Aspen defaults to say "don't look at me" if just about any single thing is "wrong" in the sensory data.

A heating element may have burnt out on Pitot heat. Maybe can see it on the amp meter, maybe not. Really tough to be diagnosing while flying single pilot IFR.

Good job keeping a cool head and getting it on the ground safely.
 
Check the pitot heat, again. Pitot heat has been known to fail in flight. Or get it checked by maintenance.

Vibration may have been ice building up on the prop. Or one of the prop heating elements may have quit working, or half of it may have quit working. Or it may have been working correctly and cycling between the prop blades throwing off ice on one blade or just part of the blade.

If you think you have ice on the prop then cycle it a few times, low to high and back a few times, being careful to not over boost or redline the rpms.

I have had an Aspen quit in the clouds before. Not comforting at all, is it? Sounds like you did good getting back on the ground.
 
If the alternate induction selection didn't change anything, it's not induction ice.The Lyco injected installations in the Cherokees and Cherokee-on-steroids are pretty resilient to induction ice. Now, at 8k in your NA Lyco, you're gonna lose power by going full rich though. What you had was pitot icing and probably trace airframe ice. For you in a non-FIKI bird, that's inadvertent icing encounter and you really ought to get outta there with a sense of urgency. That means once you saw ice form, not after your pitot blade iced up to zero knots. Even with 300HP up front, our spam cans are generally underpowered when it comes to icing.

At any rate, your element might have failed, or the breaker popped. I have a digital volt/amps multimeter in my Arrow, and I can tell with good fidelity the load and voltage of the system, and it's a noticeable jump when I have the pitot heat on versus off. Which is much more I can say about those garbage OEM ammeters that barely budge and have no needle demarcations worth a damn.

I don't find the use of pitot heat on these Piper blade elements warranted on a full time basis. I'd leave that thing off until you entered visible moisture. They tend to last longer that way. I don't think you can burn the Piper one; I sure can damage the thing on the T-38, and cause burn injury to ground crew. In any event, I believe full time use outside freezing conditions does shorten its life.

On a complete sidebar. Aspen needs airspeed to provide attitude? Oh heall naw. A solution that requires GPS ground speed or pitot airspeed to gonkulate an attitude depiction is not what I call robust. Even an electric TC treats you nicer than that. I thought the more robust software solutions had a gravity sensor that always knows the gravity vector and can solve for the attitude solution in pitch and roll. 20AMUs for two big red Xs when it counts? That's a hell of a premium for consumer grade tinker toy behavior. I digress.

Great job on keeping it blue side up and getting back to melting altitude. I would have begun the descent at the moment of ice ID, but otherwise you did good today. Now go find yourself a real attitude indicator for a backup. :D
 
This is the second time recently that I've heard about the Aspen going fault because of pitot-static ice. I don't understand why it must fail attitude and nav info in this case, seems fragile and wrong.

For ref:

 
Agree with everyone, most likely pitot heat failure due to becoming iced up. As hindsight mentioned, you can check by cycling the on/off switch and look at the ammeter, may give you an indication. Airframe vibrating a pretty strong warning you're wings and prop are icing up (besides visual checking wings) and you needed to get out before you fall out, out of control. The reason everything began working at lower altitudes was probably warmer outside air which melted the ice. Hard lesson to learn but hopefully one you'll remember and find an out next time.
 
You guys referencing the Aspens taking a s*** when losing airspeed input have a point I haven't seen an answer to. I believe the garmin G5 does the same thing. Makes no sense to X out an AI because of faulty pitot input. The only thing I can finger is must be some certification issue?
 
So would an Aspen show a red X on the ground with 0 airspeed? Some AHRS require a GPS signal, but airspeed, doesn't make sense.
 
Velocity173 said:
So would an Aspen show a red X on the ground with 0 airspeed? Some AHRS require a GPS signal, but airspeed, doesn't make sense.
Click to expand...
Aspens do not show a red x on the ground. Of course on the ground the Aspen ground speed will be fairly close to airspeed.
 
Can I ask a question - you guys have gone into a discussion about the Aspen and ice accumulation unbalancing some pieces, but I'm asking what about flying into ice?

"Your thoughts?" Yes, WTH were you doing flying in clouds with temps at -14!? That is practically the recipe for heavy icing and since you didn't talk about inflating the boots or anything like that, I'm guessing you weren't flying an aircraft certificated for FIKI. Forget about the legal quibble of whether it was known or just strongly suspected, it is a really, really dumb thing to do. The fact that you did it at midnight just adds to it.

My real thoughts - gosh, this guy could have died, I wonder if he realizes that.
 
Clark1961 said:
Aspens do not show a red x on the ground. Of course on the ground the Aspen ground speed will be fairly close to airspeed.
Click to expand...

So it's an indicated vs ground speed disparity? Even that doesn't make sense. The EFIS displays I use start to display airspeed at either 20 kts or 35 kts. Doesn't matter what GS readout is, it won't red X the whole display. Won't red X anything actually.
 
Last edited:
It also sounds to me like the pitot heat failed. The incremental decline in IAS was simply the progression of rapid ice accumulation on the tube. Ice can build quickly in temps that cold.

As flynn mentioned, this whole encounter shouldn’t have really came as much of a surprise to you. If you weren’t FIKI equipped, than I’m puzzled as to why you elected to fly through clouds at those temps.
 
Zeldman said:
Check the pitot heat, again. Pitot heat has been known to fail in flight. Or get it checked by maintenance.

Vibration may have been ice building up on the prop. Or one of the prop heating elements may have quit working, or half of it may have quit working. Or it may have been working correctly and cycling between the prop blades throwing off ice on one blade or just part of the blade.

If you think you have ice on the prop then cycle it a few times, low to high and back a few times, being careful to not over boost or redline the rpms.

I have had an Aspen quit in the clouds before. Not comforting at all, is it? Sounds like you did good getting back on the ground.
Click to expand...


That.

And careful of going full rich at altitude or even in higher DA.

Also this is the reason IMHO an aspen is only a cosmetic modification for an aircraft and shouldn't be used at night or IMC, that method of failure is complete BS. The fact the FAA shutdown navworx for having a diffrent model chipset, but doesn't do anything to aspen for a defect that straight will get someone killed just makes one scratch their head.

And stay out of visible moisture (rain, clouds, etc) when it's 0C outside unless you're FIKI, or want to become a lawn dart.
 
Let me make couple of things clear. The conditions I was in was not such that one needs FIKI . The forecast was for <50% chance of trace icing and that's what I was dealing with. From my previous experience I know this aircraft can easily handle trace to light icing. The purpose of thread was to know others experiences regarding pitot malfunctions and remedies. The control of aircraft was never in question. About the advancing the mixture, I always lean aggressively so whenever I advance the throttle I have to advance the mixture or engine will falter.

I checked the temp on pitot tube after heating it up. Its 97 d F. That doesn't sound hot enough. What its suppose to be? What options to fix on blade style pitot tube ? just replace heating element or need to replace entire blade?
Thanks
 
blueskyMD said:
Let me make couple of things clear. The conditions I was in was not such that one needs FIKI . The forecast was for <50% chance of trace icing and that's what I was dealing with. From my previous experience I know this aircraft can easily handle trace to light icing. ...
Click to expand...


Are you serious?

Keep playing stupid games, you're going to win a stupid prize.
 
Timbeck2 said:
But does it get hot enough to burn your hand?
Click to expand...
I’m not dumb enough to put my hand on a heated pitot tube. That’s what thermometers and other people’s hands are for.
 
Yikes. This thread saves me about $20,000 (Aspen and installation). If I can find a few more threads like this, I’ll be able to afford a certified FIKI plane of my very own.

The pitot tube should be capable of injuring anyone who grabs it. 97F sitting still in the hangar would melt ice off eventually, but it is probably not going to keep up with ice accumulations at -14C (~0F) moving through the air.

The appropriate response to icing in cruise is to escape the icing conditions without delay. You should listen to the advice here about that. Icing forecasts are just forecasts. You can fly when there is 50% chance of icing, but when actual icing happens you need to get out. Your logic is a lot like walking around all day in a rainstorm without an umbrella and claiming you are actually dry because there was only a 50% chance of rain.

Frankly, once you start to pick up airframe ice, you are flying in known icing conditions. Continuing into those conditions without even trying to get out of them is intentional flight into known icing. If you survive the incident that doing this causes, you may want to have a better response to the investigators than saying that the chances of icing were less than 50%.

Your response to the advice in this thread is also a good example of a couple of hazardous attitudes that the FAA even tests on. Anti-authority, invulnerability, and macho all apply. The reason to test on these is because they have already killed enough people, especially people whose day jobs either reward or tolerate these attitudes.

Your pitot heat is broken. But so is your ADM. The latter is the deadlier and more immediate of your problems. Nobody is telling you this because they think they’re better than you, which is how you seem to take it. They’re telling you this because they don’t want you to kill yourself or others, as you seem intent on doing.

Edit: I know that you will likely disagree with me and everyone else who thinks you’re not flying safely. If so, please call our bluff and file a NASA report to call attention to the serious risk that the Aspen failure mode you observed poses.
 
Last edited:
iamtheari said:
Yikes. ...The appropriate response to icing in cruise is to escape the icing conditions without delay. You should listen to the advice here about that. Icing forecasts are just forecasts. You can fly when there is 50% chance of icing, but when actual icing happens you need to get out. Your logic is a lot like walking around all day in a rainstorm without an umbrella and claiming you are actually dry because there was only a 50% chance of rain....
Click to expand...

Nailed it. When your argument is that the forecast wasn’t what you ended up in, and thus the forecast is correct and what you are actually seeing is not, your ADM is what a friend refers to as “messed up like a football bat.” Sometimes referred to as suffering from acute rectal-cranial inversion...
 
iamtheari said:
The appropriate response to icing in cruise is to escape the icing conditions without delay. You should listen to the advice here about that. Icing forecasts are just forecasts. You can fly when there is 50% chance of icing, but when actual icing happens you need to get out.
Click to expand...

Agree. But sometimes the fastest way out is straight ahead. Not all the time, but in certain conditions. Like in some certain conditions the fastest way out is turning around.
 
iamtheari said:
Edit: I know that you will likely disagree with me and everyone else who thinks you’re not flying safely. If so, please call our bluff and file a NASA report to call attention to the serious risk that the Aspen failure mode you observed poses.
Click to expand...
From Aspen's user manual:

The PFD has been tested to be robust to these failures, either by being tolerant to incorrect pitot or static inputs, or by detecting and annunciating a degraded attitude solution. When connected to an IFR-certified GPS, the system is further able to detect and annunciate blockages in the pitot system and will fail the attitude solution before it becomes degraded. In that case, the system will red X the attitude and heading information, and display a CHECK PITOT HEAT message as a reminder to the pilot to check for ice accumulating on the pitot probe.

A NASA report would be a waste of people's time.
 
Most pitot heaters will burn. My Velocity and my old AA-5 wouldn't burn my hand but they do feel hot to the touch. I've flown aircraft with windshield anti-ice that only gets up to 109 F. So, it doesn't have to be scolding hot to prevent icing. 97 does seem a bit mild though.

Personally, I wouldn't fly in forecasted trace-light in a light GA without wing / tail de-ice. Done it in helos but the blades generally have enough friction to melt it. But, your aircraft, your ADM.
 
Last edited:
Clark1961 said:
I’m not dumb enough to put my hand on a heated pitot tube. That’s what thermometers and other people’s hands are for.
Click to expand...
What you should be doing is turning the pitot heat on during your cockpit preflight, then turn it off, exit the cockpit and check the pitot with the back of your hand.
 
blueskyMD said:
Let me make couple of things clear. The conditions I was in was not such that one needs FIKI . The forecast was for <50% chance of trace icing and that's what I was dealing with. From my previous experience I know this aircraft can easily handle trace to light icing.
Thanks
Click to expand...
You said your aircraft isn’t FIKI, but do you have any ‘de-ice’ equipment, or just pitot heat?
 
Fearless Tower said:
What you should be doing is turning the pitot heat on during your cockpit preflight, then turn it off, exit the cockpit and check the pitot with the back of your hand.
Click to expand...
Not me swabbie, i gots a thermometer.

And while it might be okay to propose a procedure it certainly isn’t your place to tell another pilot what to do.
 
Fearless Tower said:
Oh, I sorry Snowflake. Just sharing a procedure from the Checklist.
Click to expand...
That would have been something along the lines of: the checklist from the Beech suggests...

You obviously failed to do that and had to respond in denigrating fashion to constructive criticism. Tsk, tsk.
 
blueskyMD said:
Let me make couple of things clear. The conditions I was in was not such that one needs FIKI . The forecast was for <50% chance of trace icing and that's what I was dealing with. From my previous experience I know this aircraft can easily handle trace to light icing.
Click to expand...
You’re a braver man than I am. I’m sure your insurance company wouldn’t have been happy with your decision.
 
Clark1961 said:
That would have been something along the lines of: the checklist from the Beech suggests...

You obviously failed to do that and had to respond in denigrating fashion to constructive criticism. Tsk, tsk.
Click to expand...

Well, what kind of aircraft do you fly that would produce a burn during a quick preflight check? Plenty of aircraft have the procedure that FT suggested.
 
Name calling om internet is unfortunate . Let me assure you that the message does goes across without name calling. But POA is not an exception its all over the net . It shows how these people were treated growing up.
I have 1700 + hours, all in GA aircrafts. But I still consider my next hour to be the most important. The forecast always calls for icing condition whenever there is any cloud in the sky with temps in freezing range. Not to fly with any icing forecast is always defendable. I am not oblivious of GA risks. Reading NTSB accident reports is my favorite pass time. Nothing in the life is risk free. I personally believe in taking appropriate risk with plenty of caution. I knew that there is out if situation gets bad. As I said the conditions were broken ceiling with high OC. I never lingered around in icing. I asked for vectors in clear air and I quickly got diverted and started the decent to clear air and within very short time I was in clear with no more ice accumulation.
And that's all I have to say about this
 
Here's a question- where was the freezing level in the area at the time of your flight? My go/no go for IFR in regards to icing is if the freezing level is below (or close to) the MEA of my intended route it is a no go flight for me. Simple as that.

I wouldn't hesitate to fly through a cloud if the OAT at the altitude I was currently at was below freezing ONLY if I knew there was warmer air below me could get to in a hurry if needed. If freezing level won't allow that, then there aint no way I'm playing that game.
 
Getonit said:
I believe the garmin G5 does the same thing
Click to expand...
My understanding is the G5 doesn't do the same thing. It should still use the gps ground speed and give you attitude reference.
 
Last edited:
@blueskyMD thank you for your post. This brought up good discussion/thought processes about those of us that have to fly in colder climates. I for one am extremely happy I didn't go with the Aspen. I had no idea until your post and watching the video @George Mohr posted that a blocked pitot would kill the whole thing. No way that otherwise great piece of equipment deserves to be in the primary spot of an a/c with that kind of failure mode (my opinion). I just researched about the G5 after you brought this to light and it appears that I will be okay...even though I may try to cover my pitot tubes to verify what kind of failure I'd get if both of them iced up.

My question reference the vibration, do you have heated props? Did you turn them on? Did you try to cycle the props?
 
I'm frankly surprised people willing to sink 15AMUs installed on these consumer grade toys are surprised by the consumer grade nature of said toys. It's not like the airspeed dependency of these "differential equation solved" attitude depictions is a state secret. The problem is that such criticism always gets cut at as socioeconomic envy. Hey man, no skin off my back; I'm not the one out 20 AMUs while getting to the same destination as the one 20Gs lighter in the wallet with two red Xs in IMC. The class envy accusations I don't have much time for though. Don't want to listen to objective criticism of these GA computer toys? Eat cake then. How's that for a class envy retort....

For the uninitiated. Attitude depictions on these all-in-one tinker toys are based on computer code that solves for the pitch and roll values, based on acceleration information from consumer grade MEMS accelerometers aligned in certain pre-known orientations relative to the box as-installed. Where they proceed to cheap out is in establishing the gravity vector, which is needed to "align" the solution against what can kill you. Toys like the early versions of the RCA 2600 didn't use pitot or GPS inputs at all, making it all MEMS based math, and the precession during acceleration made my mechanical AI look like Apollo Lunar Module docking in quality. Instead, they get around that problem by using airspeed, or worse, GPS speed, to attain that fourth and "caging" variable. Problem is that now No speed means no gonk, means no fancy display, means a red-X four fingers shy of a high-five for you when the chips are down. Oops. Guess ripping out that brass pneumatic AI wasn't such a hot idea after all.

For those who don't fly behind toys, the electronic depictions of attitude are based on no-kidding ring laser gyros that provide direct angle rate information in all three axis by measuring frequency interference of two counter-propagating laser signals (Sagnac effect). Which means, for those keeping track, no airspeed data is needed to provide direct attitude solution. Furthermore, GPS info is used to only update the nav position of the ship, aiding the accelerometers portion of the INS to keep nav position integrity. Not that it needs much after initial alignment, especially in short duration flights. Though airspeed information is embedded into the ADC on most of these INS solutions, loss of airspeed data means Rick-all to the attitude depiction. This is what airliners and birds of killing alike fly behind, and not your Toys-R-Us accelerometer-based Aspen/G5/Dynon.

Even mechanical brass has vanes that inherently point at the gravity vector in order to divert pneumatics and re-cage the presentation card in front of the gyro. Aspen doesn't even have the electronic version of that, which is what it would otherwise need in order to not necessitate airspeed to solve the equations for roll and pitch without a crutch.

So to reiterate. When you buy a garmin/aspen box, you're not buying a RLG. As such you should consider the manner and severity of conditions in which you launch without a robust attitude information backup. I personally would prefer a brass gyro for a backup, but Needle-ball-airspeed is legal too I suppose. Though the latter is ill advised for the weekend warrior imo, if the stats that led to AC 91-75 are to be taken at face value.
 
Last edited:
Radar Contact said:
My understanding is the G5 doesn't not do the same thing. It should still use the gps ground speed and give you attitude reference.
Click to expand...

If true, it appears you have one backup to the airspeed crutch, otherwise it's the same MEMS based approach to attitude. I've seen what happens to GPS derived speed at high angles of bank in the Dynon D1 series (portable, GPS only input). Middle finger.

So. Probabilities of having both pitot (icing or otherwise) failure and GPS outage in level flight in the same flight are pretty low, but in banking flight it could bite you depending on the GPS antenna installation position. Caveat emptor. I'd still keep my brass, but that's just me.
 
You must log in or register to reply here.
Back
Top