An anonymous forum to allow you to share those moments in flying that caused you concern. You can post without registering a username, registered users can log out to post
By Anon
#1345877
I am a relatively new PPL with only a few hours logged since passing my skill test. I decided to fly on a clear cold winter’s day. The weather looked good, very little cloud, 10 km+ vis wind 4 kts down the runway. The only thing of note was an air temp of +3 and a dew point of +1.

I hadn’t flown since before Christmas and planned to just do a local bimble, with some general handling and maybe a few touch and goes on return. On checking the aeroplane (PA28), there was evidence of some light frost on the upper wing surfaces which was rapidly melting and easily brushed off with a gloved hand. The club has de-icing kit available, but I didn’t think I needed it, so didn’t take it outside with me.

After all the pre-flight checks, the engine started somewhat reluctantly – despite being primed and turned over by hand before engaging the starter. Once up and running I let it warm up gently and then called for taxi clearance (full ATC airfield). Taxyed to the holding point and carried out power checks without any problem. Got take off clearance and lined up on the runway and started the takeoff roll. Airspeed indicator showed acceleration as expected and I rotated at around 65 kts indicated. So far, so good.

As I climbed, I glanced down at the ASI which showed it dropping below 60 kts. I immediately lowered the nose and the speed gradually increased to just above 60 kts indicated. I checked the throttle was fully open and rpm was as expected, checked mixture was fully rich and carb heat was off. Still only showing above 60. Looking outside it was fairly obvious that the scenery was passing at more than 60 kts, so I continued the climb with about 5 degrees nose up. Something wasn’t quite right. Pitot heat! I had gone through the checklist during the power checks and the OAT was showing as +5, so I decided to leave the pitot heat off at before departure.

With pitot heat on, I continued with a shallow climbing turn and levelled off at circuit height. As I levelled out, the ASI showed just over 90 kts. That’s it, I thought, ice in the pitot tube. Won’t forget that one again! I thought about immediately returning, but the ASI was reading correctly now, probably just a bit of ice or moisture in the pitot tube. I continued a gentle climb to 2,100 ft. Time for some general handling. I started with a 180 to the left, then one to the right – quite happy not to lose any height in the turns. Next was a few stalls.

On climbing to my planned 3,300 ft, I noticed that the ASI immediately dropped below 60 kts again. Obviously attitude related. I decided that I couldn’t rely on the ASI. I needed to get back to base and land, but with an ASI I couldn’t rely on.

I decided to continue my climb and carry out a couple of stalls. I tried a clean power-off stall. Carb heat on, reduce the throttle to idle and keep some back pressure on the yoke, the ASI dropped as normal. The stall warner sounded and then the buffet before the full stall. Nose down, power on and recover. On lowering the nose, the ASI leapt to 120 kts. I wasn't doing anything like 120. It was obvious I was correct in assuming it was attitude related. Nose up under reads, nose down over reads, Straight and level unreliable.

Returning to base, there was no-one else in the circuit, so I asked for, and got, a left base join. I decided it was better to be high and fast than low and slow. There was a nice big runway, so I landed with a few knots more speed than I would have had with a working ASI, but there was enough runway to allow this.

I have decided to remain anonymous because I am sure that I will be slated by the sky gods on here for not returning immediately or for having an incompetent instructor who didn’t teach me to recognise speeds by listening (my instructor was excellent, incidentally). I don’t think that every eventuality can be covered on the PPL course. What my instructor did teach me was to remain calm, try to analyse the problem and work around it.

Was there anything I could or should have done differently?

After reporting the defect to the engineer, he said that it was probably fluid in the pitot tube.
#1345891
I don't think I'd have gone anywhere near the stall (on purpose) with an ASI I believed to be duff, or am I misunderstanding the sequence of events?

Apart from that You managed as best you could and didn't bend anything - a result. Are you going to go up with a post it note to put on the ASI and get used to speeds produced by different combis of power and pitch next time out?

I haven't done that in a while either. Maybe I will too!
User avatar
By Keef
#1345892
Like Leia, I'd not have gone near the stall, and I'd probably have returned and landed without further ado.
That said, flying without the ASI is good practice, although I'd prefer to do it with a serviceable ASI covered up.
By Anon
#1345898
My reasoning for trying a stall was to see what the ASI might show and try to see what warning I would get approaching a stall without an ASI (stall warning buzzer, buffeting) rather than have an unexpected stall on approach without any warning.
User avatar
By AndyR
#1345905
Indicated airspeed not required to check stall characteristics. It's all about angle of attack. Sensible course of action in my book. Certainly nothing to panic about. Power + Attitude = Performance.

Well done for dealing with it and landing safely.
User avatar
By Miscellaneous
#1345970
Leia, Keef, what's your thinking about staying away from stalling? I'm struggling to see any gotchas, but can see benefits?

What am I missing?

Misc.
User avatar
By Keef
#1346008
Mine's the "self-preservation" instinct. Cowardice Prolongs Active Life, and all that. If the ASI isn't working, what's the cause and what else is misbehaving? I know the stall speed of my aeroplane, and I know how it feels as it approaches the stall, so don't really need to test that in an ill aeroplane. Get it back on the ground safely, without taking unnecessary risks, and then check stuff in the safety of the hangar with experts around. It might be a wasp in the pitot, or it might be the pitot and a piece of wing that's breaking away and getting ready to fall off, or a range of other things.

The probability is that nothing else is wrong, but I'd rather an engineer told me that. I'm the bloke who had an engine start to run rough over the channel, diagnosed it, and flew home. The diagnosis was wrong, and the engine died completely on the rollout after landing. ILAFFT.
User avatar
By leiafee
#1346039
Miscellaneous wrote:Leia, Keef, what's your thinking about staying away from stalling? I'm struggling to see any gotchas, but can see benefits?


I'd have been afraid of...

...Overspeeding in the recovery if faulty ASI and I already knew (as the OP states) I wasn't certain about how else to judge the speed in absence of ASI.

...the unknown problem causing the ASI to misread also causing something else unexpected to happen or affecting the stall characteristics. I may have suspected ice but with the failure of heat to cure it I'd worry about something being bent and maybe making the handling at the stall wierd.

I couldn't see the benefit of seeing what the ASI reads in the stall if I already knew it was wrong and I'd no real evidence to suggest it was CONSISTENTLY wrong by X amount.

I saw more risks than benefits so wouldn't have. I can see the arguments both ways though.
By Anon
#1346043
Keef wrote:I know the stall speed of my aeroplane, and I know how it feels as it approaches the stall, so don't really need to test that in an ill aeroplane.


I am a newly qualified PPL. It's not my aeroplane and I don't have thousands of hours flying it. I know the stall speed. I just wanted to ensure that I would have some warning approaching a stall, ie stall warning buzzer, and how the aeroplane would feel, rather than find out on final approach that the buzzer wasn't working either. (It was checked and working on the ground during my pre-flight checks).

Anon wrote:I have decided to remain anonymous because I am sure that I will be slated by the sky gods on here for not returning immediately


Keef wrote:Get it back on the ground safely, without taking unnecessary risks, and then check stuff in the safety of the hangar with experts around.


Bingo! We have a winner... :wink:
By Anon
#1346121
Keef - I hope you took that comment in the spirit it was intended. There doesn't appear to be an "only joking" smiley...
User avatar
By Keef
#1346224
Always laughing, Anon, and skin like a rhinoceros (comes of years of Adminning on here).
#1346577
Hi anon, and thanks for the candid post.

You had a frozen airframe so it would have been safer to switch the pitot heat on before takeoff. I use a rule of thumb that if the OAT is going to be 5 or less during the flight use pitot heat from the start.

You appear to rely on airspeed quite a lot so it would have been safer if you had circuited and landed straight away. Continuing the flight and experimenting with stalling with the distraction of a malfunctioning airspeed indicator (and possibly altimeter and VSI) is something I would not recommend.

On your next reval hour do a flight with no reference to your ASI as you did (hopefully) during your training to remind you that pitch, power, balance and flap setting will always give you the airspeed you seek.