ASI unservicable! Now what do I do?

[mary meagher]

Okay, it was only a glider. But it does get your attention! This sort of thing would never happen in a power plane, would it?

All my fault, actually. When I parked the glider overnight without derigging, I taped up the pitot and the statics with WHITE TAPE. Wrong tape. Red or black might have been noticed. Removed the static tapes before flight.
Forgot to remove the pitot tape.

Very very turbulent airtow for first 500 feet. Other pilots noticed that as well, so wasn't just me. After hanging on for grim life, began to wonder how fast this blankekty blank tug was flying, so glanced at the ASI. It read zero.

All right. I knew right away what I had forgotten to do. As we were still boring through the atmosphere, no doubt we were doing better than zero mph. Decided to hang on to cloud base, 2,500. And then think about it.

Yes, the alt seemed ok. Cows about the right size. The vario said we were in lift, turned, and the alt. recorded improvement in altitude. So 2 out of three not bad.

I practiced gentle stalls. Simulated approaches with and without airbrakes. Even in a slick glass glider, the wind noise gave a good indication of airspeed. So what the heck, I flew locally for 2 hours, and then made my most careful circuit and approach in years.

Confessed to the CFI. Red tape from now on.

[BackPacker]

This sort of thing would never happen in a power plane, would it?

Aeroperú Flight 603 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/AeroPeru_Flight_603)

You were relatively lucky that you flew with a covered pitot tube. This means that the altimeter and the VS/vario will still work because they rely exclusively on static port data.

If your static port would have been covered, not only would you have been screwed in the altitude/vs/vario department, but in the speed department as well, since the ASI relies on the difference between pitot and static. Far more dangerous. Most power planes have an "alternate static" just for this kind of situations, usually a valve which vents the static tube into the cockpit. (Unpressurized aircraft only of course.)

Power pilots regularly practice instrument failures of any kind and particularly in a small airplane, it's not that hard to setup the aircraft for a slightly fast approach speed. After all, you know the approximate RPM and trim settings from earlier landings, the sight picture and everything. And as you correctly mentioned, you know (or try out) what exactly the stall feels like in that particular aircraft.

Then it's just a matter of having a long enough runway so that you have time to bleed the excess speed off over the runway. But you wouldn't want to do a short-field landing without an ASI.

As an aside: did you have any kind of GPS on board? This should be able to tell you your altitude as well, more or less.

Anyway, well done! I guess the pitot and static ports are now firmly back on your preflight checklist?

[jamestkirk]

Firstly. If we don't make mistakes we cannot learn. Now that red tape has been introduced at your gliding club, it will probably prevent others doing the same. So there is a definate positive from your experience.

Remember PUDSOD Pitot blocked, Under-read in a DX Over-read in a CX. Static blocked, Over-read in a DX, Under-read in a CX.

You probably already know that.

[Mark1234]

Fly by trim/ stick position. Particularly in a single seat glider where there's not much variation in CG. Trim sets speed (hands off stick). Find stall trim/stick pos, trim a bit forwards. That'll give you a rough approach speed. Better still, make a note of your trim position at approach speed when the ASI *is* working, even mark it. Let go of the stick it'll settle to that speed. If you let go and it noses down, too slow, etc. Wind noise is a biggie in a glider - I know I had to do circuits with the ASI covered and Alt covered before being let lose.. though that's easier in a draughty old K13.. Opening vents or the dv panel will make more noise and might help.

Same would also work with a powered a/c. Trim sets the airspeed, power will determine whether you climb or descend at that airspeed. I wouldn't be so confident doing it in a powered aircraft though, and messing with flaps and gear will corrupt that.

For my part I can't remember that many mnemonics, but I do remember how the pressure instruments work. A couple of minutes thought will tell you what it's going to do. Total failure is far less trouble than a more subtle one - The big problem is figuring it's giving bad data when it hasn't actually ceased completely. For instance flying partial panel knowing the AH has failed you still look at the d*mn thing. A postit is very handy to cover something that's misbehaving - a good visual reminder to ignore the bad data :)

[Gertrude the Wombat]

This sort of thing would never happen in a power plane, would it?

In fact no, because you check the ASI during the take-off run and would abort the take-off it it was stuck at zero.

What are the options for aborting a tug launch when the glider pilot sees something he doesn't like?

[18greens]

I wonder how many power pilots do check the ASI ion the takeoff run Also why is it not a check in a glider?

Theres also the point that all aircraft are fitted with an alternate static even if it is not labelled as such. Break the VSI glass and you have a very expensive alternate static.

Remember in the old days aircraft did not have instrument and on a good day with a horizon no instrument should be necessary. A different matter in IMC.

[gpn01]

I wonder how many power pilots do check the ASI ion the takeoff run Also why is it not a check in a glider?

When you're on the ground and stationary in a glider there's no way to reliably check to see if the ASI is working.

In gliding you're tought to fly by attitude and you quickly gain a feel for the right picture for various speeds. So an ASI failure isn't necessarily a big thing - but does focus the mind a bit. The trick is to remember to keep flying the aircraft and don't become completely fixated by an instrument failure. An altimeter failure isn't a big problem either (providing you're not near the base of airspace). Glider pilots don't use the altimeter for landing - they're taught judgement skills (often part of the training is to blank off the altimeter to make sure it's not being used as a reference - this develops a particularly useful skill for when you've taken off from an airfield that's a different height from where you're landing). Vario failure's not a problem either - if the houses are getting smaller, you're climbing!

[S-Works]

I wonder how many power pilots do check the ASI ion the takeoff run Also why is it not a check in a glider?

Well I do. Its how I determine the unstick speed has been reached. Do others just cling on for grim death and wait for the aircraft to leave the ground?

[Big Pistons Forever]

When I am teaching the circuit and landing I regularly cover the ASI to stop the students from chasing the ASI and instead concentrating on flying the correct attitude. As we chug around the circuit I ask them what they think the airspeed is and then uncover the ASI to check. They are continually amazed at how close they usually are. For my CPL students I do a complete circuit and landing with the ASI covered.

[KeesM]

Lesson learned and no harm done, good job.
I had blocked static ports a couple of times in SEP aircraft, no big deal while VFR.
Just keep flying the plane.

[englishal]

GPS also give you ground speed, so if you have a good idea what the wind speed/direction is you can approximately guess your airspeed, at least on final - so you can tell if you are way overspeed anyway.

Still, best advice is to learn to fly by "feel", once I am on final, I only glance at ASI occasionaly, and from short final don't look at it at all.

[Crash one]

I wonder how many power pilots do check the ASI on the takeoff run
I seem to check mine halfway across the plowed field next door at about 50ft:ugh:
I have also left the cover on twice:ugh:
It consists of a block of wood painted red & yellow stripes with 2 holes in to cover both pitot & static & a flag that says "Remove before Flight" I know it is there because I made the thing, thinking it was a good thing to have!:ugh:

[RatherBeFlying]

I am surprised that taping the pitot and/or static is normal practice anywhere. It's simply asking for such an incident.

Yes in many gliders and power a/c, a pilot familiar with the machine will get around the circuit quite happily. I once discovered a blocked pitot while the end of the runway was rapidly approaching and decided it better to take it into the air than hope I would stop on the remaining downsloping runway.

It can get complicated in flapped gliders.

I would not tape ports or do anything else affecting airworthiness without leaving a note taped to the stick.

[AlastairMutch]

I've tried it in both glider and power :O.

With the glider it was when I had left it out under covers without sealing the pitot properly. The water that had leaked into the pitot system in the rain was enough to give some very funny readings on the ASI (winch launch so didn't abort) with the speed jumping about in 10kt steps. I flew on the hill for an hour or so just ignoring the ASI and then did a slightly faster than normal approach and landing without any great problem. Now I'm very careful to block off the pitot when it's left out under covers. I also tape over the upper statics in any showers when on the ground waiting to fly as they are on top of the fuz and vunerable to water ingress. I find a bit of grass under the white tape over the static is enough of a reminder.

On the power side it was with our AA5 in the winter as a result of ice in the static vents. The plane is normally normally parked outside under covers. With a vent on each side of the fuz you wouldn't expect it was possible for both to become blocked with ice. Nothing untoward on preflight check, taxi or take off but the problem became obvious in the climb as I had to lower the nose to maintain airspeed until I just stopped believing it. The altimeter stopped rising in the climb too.

There's no alternate static in the AA5 so I just ignored ASI and altimeter and flew by power and attitude. A quick return to the field and a bit of heat on the static vents soon sorted it out. Nice VFR conditions so no need for anything as extreme as breaking the VSI glass.

Alastair

[BackPacker]

I find a bit of grass under the white tape over the static is enough of a reminder.

Brilliant solution! (At least, on a white glider.)

[Mark1234]

I wonder how many power pilots do check the ASI ion the takeoff run Also why is it not a check in a glider?

Yep, I do, along with ensuring it's developing the expected number of RPM.

However, in a glider it's a little more tricky - you're bouncing along what usually feels like a ploughed field - the wheel is 6 inches under your butt, trying to fly in formation behind the tug on the end of a piece of string. You'll become airborne a long while before the tug, then you have to fly 2ft off the ground, in formation (remembering in a crosswind you'll have to counter drift well 'cos the tug is still attached to the floor..) I'm not saying it's not possible, or you shouldn't but it's a very head out occupation, and taking a good look is less practical.

Abort options: Pull the yellow knob (tow release) and park it; same as a cable break. Land ahead, make a low level turn and land across the field, over the hedge and into the next, or complete a truncated circuit / turnback. In many ways the glider's got a lot more options; you can do more with less height.

[IFMU]

I used to own a Blanik L33 solo. I left it tied out. After a while, I seemed to get a lot of water in the static ports and I would have pitot-static failures until I landed and cleared it out. Had pitot blockages too, even though covered. That one was from cutting the grass. How the clippings got that far I'll never know. I would miss the vario but never the airspeed. No way would I do a PTT (premature termination of tow) based upon no airspeed. I think it's a lot safer to sort it out at altitude, especially given our strip is short and ends in a 800' drop off. I gave up on the suction cups I had and took to taping the static ports. Guess what was handy - white tape. Never forgot it though. Now I own a 1-35 and it seems free from water in the pitot static system.

I had the flapper valve that covers the pitot tube freeze shut one time in our C140. It was fine during preflight, in our heated hangar. Water that splashed up from the tires must have gotten it. In the taildraggers I don't usually look inside during the takeoff roll. In the arrow I do especially when playing the IFR game. Since I was aloft and in the easy part of the flight, I thought I would see if it would pop open during the descent and higher airspeed. Never did. After I landed I freed it up. There were no puddles at the airport I flew to, just an inch of snow.

I would say anything that I fly often, I am not overly concerned with an airspeed failure while in VFR. I can pretty much hit the speeds without looking, just by attitudes & power settings. When I fly in the back of a 2-33 I can't see much anyway, especially with somebody big up front. Like any other failure, the number one thing is to fly the airplane, and not do something that makes an inconvenience into a real problem.

-- IFMU

[john_tullamarine]

The old adages about pitch and power are dead true.

For sim training, I always made sure that transitioning students could takeoff in low vis, suffer a TOTAL pitot static failure during the takeoff rotation (including everything I could fail from the back relating to speed and height and slope information). Requirement, without any assistance or prompting from me, was for the student to get him/herself around to a landing via a low minima ILS.

All done on the A/H with known power for the configuration to achieve a flight performance (speed and climb/descent).

The only difference for a lightie is that, if you don't have an A/H you need to be visual for attitude. I'm sure we were all taught to fly initially by matching the desired window picture to the horizon ?

The first time it's a tad anxiety producing but after a couple of goes just another walk in the park.

If you haven't done a flight with the LHS clocks U/S (it's a bit silly for the instructor or safety pilot to fail his side clocks) it is a useful (I would say essential) training exercise and might just save your neck one day in the future. Likewise a few under the hood circuits are excellent training value .. 0/0 landings being talked down by the other pilot is an interesting exercise for the first couple of circuits.

Most of the story is in the thread -

the wind noise gave a good indication of airspeed

"Wind in the wires" goes back to WW1 times. As an anecdote, a strategic bomber was on test with a mod on the side. Unpredicted and undetected problem was that the PEC was thrown to the winds. Picked up on takeoff roll by the TP who recognised the mismatch of sounds and ASI reading.

Most power planes have an "alternate static" just for this kind of situations, usually a valve which vents the static tube into the cockpit. (Unpressurized aircraft only of course.)

All certificated aircraft should have an alternate static source - Boeings etc, included.

A postit is very handy to cover something that's misbehaving

Absolutely - even lick the back of a sheet of paper and it will stick onto glass reasonably well .. and enough for the purpose.

What are the options for aborting a tug launch when the glider pilot sees something he doesn't like?

Tug pilot should release and then judge his recovery to minimise the risk of the glider overrunning the tug. Becomes a problem if the problem occurs just after liftoff .. in this case most of us would hang on until we had the glider into a position where a release wasn't going to cause him/her too much anxiety. If the glider pilot doesn't like how things are progressing he/she can pull the bung as an alternative. The only time I had this sort of situation happen was following the glider's failed attempt to release .. in the subsequent turn, he put me into a low level spin and we both released .. losing the cable in the process. My concerns at the time were more with the leaves and branches in my field of view rather than the glider.

[Dan Winterland]

Luckily, as a glider pilot you will be used to looking out of the window and flying attitudes. Shouldn't have been a problem.

As for how likely would it be in a power aircraft. Quite is the answer - as it's happened to me three times! Once, an insect commited suicide down my pitot tube. I just flew power against attitude and used the groundspeed readout on the DME as a guide for the approach. No big deal. The other two times were identical incidents in a military trainer where the ASI capsules used to rupture when we did inverted spins. But the aircraft had an AoA guage which was a real aid to flying an approach.

[ExSp33db1rd]

Forgot to take the pitot cover off the Turbulent. ASI started to increase OK then was airborne - doing 140 kts, when the Vne is only 104. Realised immediately, but was still climbing, so wasn't stalling, so pushed the nose down a little bit to give a bit of fat, waited for the cows to look about the right size and set cruise power,turned downwind, and eventually on to finals, set normal approach power, threshold in windscreen looked OK, maintained steady glideslope, no sweat. ( except that I was - a bit ! )

How did I let myself get into that position ? Long story, basically let myself get distracted and out of sequence.

[India Four Two]

Gertrude asked What are the options for aborting a tug launch when the glider pilot sees something he doesn't like?Here are some considerations from the tow pilot's point of view. It happened to me on my first flight of the day at the Canadian Nationals a few years ago. I noticed during my RPM and airspeed check before lift off, that the ASI needle was bouncing around zero. Since I had an open-class glider behind me with water ballast, I made a quick decision to continue the flight, rather than have the glider run into me on the runway as I stopped. I continued the climb, using attitude for speed control and by the time I reached release height, the needle had come up to the correct speed.

We had had a big rainstorm the previous evening and water must have entered the pitot tube, which on a Bellanca Scout, angles slightly upward on the ground. During the flight, the dynamic pressure must have slowly displaced the water into a water trap in the system.

Ironically, each previous day, I had made a quick circuit before towing. For some reason on this day, I didn't!

Here's a picture of the pitot/static system, with a different reason for ASI failure. Unlucky bee!

http://i30.photobucket.com/albums/c309/india42/Beeinpitottube.jpg

[Fitter2]

I had virtually the same problem as India Four Two a while back, towing a Skylark 4 glider out of Nympsfield (Bristol Gliding Club) with a Jackaroo (4 seat Tiger Moth conversion, for those too young to remember) at a competition.

At about 100 ft over the edge of the airfield, crossing the ridge, a significant bit of turbulence must have displaced some trapped water, asi flickered and dropped to zero. It would have been unsociable to dump the glider, and unnecessary - I carried on with the tow (and subsequent circuit) on attitude and power, and parked while disconnecting the pitot and static lines and blowing out the water.

I declined the offer to carry on towing before fixing the problem, and the competition director quite understood my point of view.

[Tmbstory]

Remember the approximate attitudes for power/ flap configuration and you will not be too far out from normal parameters.

A tip for the Cessna 150/152/172 aircraft, when on the approach to land ensure that the ventilator tube into the cockpit from the wing is opened. You can hear the change in sound as the centre of pressure moves forward as the angle of attack increases. It used to be a good way to demonstrate a precautionary approach with a covered or failed Air Speed Indicator.

[mary meagher]

The go - no go decision is exactly the same for any takeoff, glider, tug, light aircraft or Boeing. It has to be made at the most awkward moment!

Thank you for all your comments. I've been thinking about my experience while driving back and forth from the airfield, and realise now that I was being economical with an important detail of PILOT failure on this flight without a serviceable ASI.

The overloaded mind effect.

I do a lot, and I mean a lot of my flying in the back seat of a training glider, the good old Kl3.

On this occasion, rigged the Pegasus single seater which I had flown only 4 times before this season, and in a hurry to get launched. So overlooked the white tape on the pitot tube. Correct decision not to abort. For all kinds of reasons. Thinking about best plan to do after releasing. Followed tug to cloud base. And absolutely BLANKED on what knob to pull to release from the tug. That actually was a moment of panic. Being in a different glider from my customary steed, it of course was not in the usual location. After a moment of complete blank, I said to myself "LOOK AT THE KNOB BEFORE YOU PULL IT, STUPID WOMAN!" At which point the British Gliding Association requirement came to my rescue. All release knobs in gliders are painted YELLOW. I located the correct one to pull and pulled. So this story ended happily.

But my moment of panic was forgotten in the subsequent management of the flight, and I only retrieved it to mull over on the drive home, and now share it with you, my electronic friends!

Mary

[Mark1234]

A tip for the Cessna 150/152/172 aircraft, when on the approach to land ensure that the ventilator tube into the cockpit from the wing is opened. You can hear the change in sound as the centre of pressure moves forward as the angle of attack increases. It used to be a good way to demonstrate a precautionary approach with a covered or failed Air Speed Indicator.

So that's what causes the wheeze in the flare... often wondered!

[Croqueteer]

:ok:Power + attitude = performance. Know your aircraft.

[oversteer]

CFI suggested leaving a glider out overnight last week - he taped up all the statics. He also put a single line of tape over the ASI and altimeter, seemed like a good idea and would be an unmissable hint when you're preparing to fly.

[tggzzz]

I wonder how many power pilots do check the ASI ion the takeoff run Also why is it not a check in a glider?
They do, to avoid the kind of situation shown in these videos:
<http://www.gliding.co.uk/bgainfo/safety/winch-safety.htm>

In addition, typically before flying solo, a student glider pilot will have had to demonstrate that they can fly an entire flight with all their instruments covered up.

[cats_five]

I wonder how many power pilots do check the ASI ion the takeoff run Also why is it not a check in a glider?
They do, to avoid the kind of situation shown in these videos:
<http://www.gliding.co.uk/bgainfo/safety/winch-safety.htm>

In addition, typically before flying solo, a student glider pilot will have had to demonstrate that they can fly an entire flight with all their instruments covered up.

At my club it's a circuit with the altimeter covered up, not all the instruments.

[Mark1234]

Can't remember if I ever did it with both covered simultaneously, but I distinctly remember having to demonstrate several circuits with each of the altimeter and the ASI covered.

However, I learned something of relevance a couple of weekends ago whilst doing my tailwheel checkout on a decathlon. This particular machine was devoid of many avionics, including no stall warner. My accomplice for the training took us up to 4000ft and we did some stalls and made me take note of the stick position. It's an extension of the trim principle, and quite obvious when you think about it. Stick position sets airspeed. In unbanked, unaccelerated (i.e. 1G) flight, if you don't change the configuration (flaps, load etc), the aircraft will stall at a constant stick position. If the stick's forward of that position, it won't stall. End of story.

Now a decathlon doesn't have flaps - so we made a lot of approaches in some pretty leery sideslips where the ASI doesn't necessarily read quite right. The whole stick position thing worked rather nicely.

Just another tool..

[SNS3Guppy]

Okay, it was only a glider. But it does get your attention! This sort of thing would never happen in a power plane, would it?


A few days ago we ran an airplane around the pattern following some major work. Several squawks were observed...including no airspeed. An obstruction, most likely an insect, was discovered in the pitot system.

Twice I've experienced pitot blockages in large airplanes, when the culprit was dead insects that swelled with contact with airborne moisture. Another occasion involved a considerable amount of water in the static system, courtesy of very large WWII sized static ports and a stiff, horizontal rain. It happens.

A variety of means of handling the problem can be had. Pitch and power works great...if you've got power. If not, then the power, not so much. You still have the sound of airflow over the cockpit. You have the feel of the controls. You have the angle the wing makes with the horizon, as well as indicated pitch (if you have an attitude indicator). You may find that your aircraft settles to a desired approach speed when you simply set the trim to a known setting, and relax the controls...trim pitch to fly the desired speed, and make slight adjustments. Approach a little high in the glider, slip as needed.

The day I received my new temporary flight instructor certificate, I climbed into my rented airplane to head home...and observed a tennis ball fitted neatly over my pitot tube...after takeoff. Here I was, a newly minted flight instructor, of all things, in the air with a tennis ball over my pitot tube. I flew home, parked not far from the flying club, and removed the tennis ball (pitot tube cover).

It happens. When it does, see it as a learning experience.