DI, AI, and balance ball all not working properly...Why???
The Original Whirly
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DI, AI, and balance ball all not working properly...Why???
I'm sure I should know the answer to this, but I'm far too tired to read my CPL notes and/or work it out...
I arrived at Sleap today, to fly to Conington to see a friend. Our old C150, which lives outside, had obviously taken quite a battering in the recent gales. One of the huge concrete blocks she's tied down to had been pulled over, and she'd moved quite a bit.
I checked her over thoroughly. No obvious problems, but the trim in front of the instrument panel had worked loose. Still, that's hardly essential. Then...
When I started taxiing I realised the balance ball (if it's got a more official name, a tired Whirly has forgotten it), which has never been dead accurate, was now well over to the left. Nothing seemed to be bent or anything, and I decided if she flew OK I could live without that. Then...
Early on in the flight I realised the DI was behaving very erratically. It sort of worked, but sometimes it didn't at all. I'm fairly used to flying using the compass - do it in R22s a lot - so I decided to ignore the DI. Then...
The AI has never been 100% accurate, but usually pretty close. I wasn't really using it; in fairly poor vis I was looking outside as much as possible, but I'm sure it was misbehaving even more than usual.
She was flying beautifully; she really is a very nice C150. There was hardly any wind, so I could fly her hands off a lot of the time. All the things one really needs in order to fly seemed just fine.
So...what is/was going on? Is it one problem that's suddenly affecting all these three instruments? And if so, what?
I thought about it, decided none of them were essential, and continued the flight. Flying a longish cross country in 5-6 km vis most of the time, with only very basic instrumentation (and a back-up GPS) was...interesting. Actually it got easier by the return flight, so I guess I learned something. I even managed one of my better landings at Sleap...after failing to find it - my home airfield - till I was nearly overhead!
On balance it was a good flight and a nice day out. But I now feel totally knackered!!!
Anyway, does anyone have any ideas as to what the problem(s) is/are?
I arrived at Sleap today, to fly to Conington to see a friend. Our old C150, which lives outside, had obviously taken quite a battering in the recent gales. One of the huge concrete blocks she's tied down to had been pulled over, and she'd moved quite a bit.
I checked her over thoroughly. No obvious problems, but the trim in front of the instrument panel had worked loose. Still, that's hardly essential. Then...
When I started taxiing I realised the balance ball (if it's got a more official name, a tired Whirly has forgotten it), which has never been dead accurate, was now well over to the left. Nothing seemed to be bent or anything, and I decided if she flew OK I could live without that. Then...
Early on in the flight I realised the DI was behaving very erratically. It sort of worked, but sometimes it didn't at all. I'm fairly used to flying using the compass - do it in R22s a lot - so I decided to ignore the DI. Then...
The AI has never been 100% accurate, but usually pretty close. I wasn't really using it; in fairly poor vis I was looking outside as much as possible, but I'm sure it was misbehaving even more than usual.
She was flying beautifully; she really is a very nice C150. There was hardly any wind, so I could fly her hands off a lot of the time. All the things one really needs in order to fly seemed just fine.
So...what is/was going on? Is it one problem that's suddenly affecting all these three instruments? And if so, what?
I thought about it, decided none of them were essential, and continued the flight. Flying a longish cross country in 5-6 km vis most of the time, with only very basic instrumentation (and a back-up GPS) was...interesting. Actually it got easier by the return flight, so I guess I learned something. I even managed one of my better landings at Sleap...after failing to find it - my home airfield - till I was nearly overhead!
On balance it was a good flight and a nice day out. But I now feel totally knackered!!!Anyway, does anyone have any ideas as to what the problem(s) is/are?
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Here's a clue.......................are they pressure or gyroscopic instruments????
You're an instructor, you should know these things therefore I presume you're winding us up??
You're an instructor, you should know these things therefore I presume you're winding us up??
Do you recall whether vacuum indications were normal?
Also, just on the offchance, where there any oddities in airspeed? (I think I know the answer, but just checking).
And to be absolutely sure, you do mean the "spirit level" ball, not the turn needle ?
G
Also, just on the offchance, where there any oddities in airspeed? (I think I know the answer, but just checking).
And to be absolutely sure, you do mean the "spirit level" ball, not the turn needle ?
G
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I could understand the AI and DI misbehaving together due to a problem with the vacuum system, and sods law says that a problem with the TC / TI MAY happen at the same time, but if the "ball" is really out of wack it would seem a bit strange.....Sure your plane hasn't been bent or something? I suppose a bent airframe *could* somehow cause all three problems, (and the trim coming loose) though don't ak me how, and it'd have to be pretty bent 
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Like they said. DI and AI both misbehaving sounds like a vacuum problem. But the slip ball is no more than a spirit level, so that should be almost bombproof.
Summat odd there, Whirly.
Was the panel loose or crooked?
Summat odd there, Whirly.
Was the panel loose or crooked?
I don't want to be the best pilot in the world - Just the oldest
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Balance ball a spirit level??! 
And you an "Angry Palm Tree'" pilot?!!!
Surely this is a wind up?
If not, the ball represents the arc of a pendulum and is NOT a spirit level (hello, it's curved) and I'm shocked that some instructors are unaware of this and hope they are not passing this nonsense on to their students.
Did you check all these instruments when taxiing out or did they only start to behave erratically in flght? What did the suction gauge say?
Anyway the only way the ball can be out from the middle is if the "pendulum" is not in line with the normal axis ie is if the aeroplane is out of balance. Or maybe if all the fluid has leaked out and it's stuck? Did it feel out of balance? As for the other problems I would suggest it sounds like a vacuum problem. And a "nice C150" is an oxymoron.
Mrs IJ, a cranky instructor.
And you an "Angry Palm Tree'" pilot?!!! Surely this is a wind up?
If not, the ball represents the arc of a pendulum and is NOT a spirit level (hello, it's curved) and I'm shocked that some instructors are unaware of this and hope they are not passing this nonsense on to their students.
Did you check all these instruments when taxiing out or did they only start to behave erratically in flght? What did the suction gauge say?
Anyway the only way the ball can be out from the middle is if the "pendulum" is not in line with the normal axis ie is if the aeroplane is out of balance. Or maybe if all the fluid has leaked out and it's stuck? Did it feel out of balance? As for the other problems I would suggest it sounds like a vacuum problem. And a "nice C150" is an oxymoron.
Mrs IJ, a cranky instructor.
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The balanced turn ball being other than central would indicate you were flying in a skidding mode, possibly because someone has been monkeying with your nose trim tab, if a Cessna has one that is. It happens to me each time a professional test pilot checks out the single engine climb on my twin. They wack over the nose trim then forget to reset it.
A follow on problem is you are then tilting wings to compensate which would account for the AI showing a 'turn', and possibly would make the DI difficult to interpret.
Alternatively the airframe has suffered during the storm, and is now flying in a skidding mode. Hopeully that's not the case.
A follow on problem is you are then tilting wings to compensate which would account for the AI showing a 'turn', and possibly would make the DI difficult to interpret.
Alternatively the airframe has suffered during the storm, and is now flying in a skidding mode. Hopeully that's not the case.
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NOT a spirit level (hello, it's curved)
Mike
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Just a general comment, not addressed to Whirlybird.
Are we all carrying out proper checks before getting airborne and do we understand what the indications are telling us?
Do we know what the correct 'suction' figures are for our aircraft and do we understand that power will have an effect on the reading(s), do we do our turn checks when taxying and do we set our trims to neutral/as required before flying?
PS Whirly, I think you've posted what could become a very useful thread
Are we all carrying out proper checks before getting airborne and do we understand what the indications are telling us?
Do we know what the correct 'suction' figures are for our aircraft and do we understand that power will have an effect on the reading(s), do we do our turn checks when taxying and do we set our trims to neutral/as required before flying?
PS Whirly, I think you've posted what could become a very useful thread
Last edited by Tee; 12th Apr 2004 at 09:07.
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I would go with the above.
The trim working its way loose rings huge alarm bells for me. When linked to the fact that the plane had shifted on its tie down.
Sounds like the whole front end has managed to become warped. The ball out to the side could be because the panel ain't level any more and the dodgy Instrument readings could be because the pressure lines at the back are leaking. Giving poor vacum causing low rpm on the gyro hence problems with DI. And if the battering was enough to do that to the gyro system its not unlikely that the Airspeed Indicator might also have a leak in it as well, one of the really dangerous ones in IMC which is only a intermitant leak proberly on the static port.
And giving Whirly abuse that she is an instructor so should know better is bollocks. There is no training in the FIC to cover this sort of thing. Its all picked up by exerence. I would hate to imagine what a Intergrated oxford straight to FI(R) who doesn't have a technical background would be like. And to be honest I wouldn't had a clue with low instruction hours, but after 1000hrs flying club planes you do tend meet a fair number of technical problems. Its better she asks than keeps quiet about it.
MJ
The trim working its way loose rings huge alarm bells for me. When linked to the fact that the plane had shifted on its tie down.
Sounds like the whole front end has managed to become warped. The ball out to the side could be because the panel ain't level any more and the dodgy Instrument readings could be because the pressure lines at the back are leaking. Giving poor vacum causing low rpm on the gyro hence problems with DI. And if the battering was enough to do that to the gyro system its not unlikely that the Airspeed Indicator might also have a leak in it as well, one of the really dangerous ones in IMC which is only a intermitant leak proberly on the static port.
And giving Whirly abuse that she is an instructor so should know better is bollocks. There is no training in the FIC to cover this sort of thing. Its all picked up by exerence. I would hate to imagine what a Intergrated oxford straight to FI(R) who doesn't have a technical background would be like. And to be honest I wouldn't had a clue with low instruction hours, but after 1000hrs flying club planes you do tend meet a fair number of technical problems. Its better she asks than keeps quiet about it.
MJ
Last edited by mad_jock; 12th Apr 2004 at 10:44.
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Are we all carrying out proper checks before getting airborne and do we understand what the indications are telling us?
Its the ball that worries me, most instruments *can* be a bit flakey during taxy, but so long as they stabilize within 5 mins or so then I wouldn't be particularly worried.......saw an AI on a new plane just completely roll over during taxy once, which surprised me a bit. After 5 mis it was stable again, but I kept an eye on it. Of course the ball can be explained by the terrain you're taxying on, though if it is all the way to one side, I'd be concerned.
How were the instruments behaving? You say the ball was over to one side, was it way over? What about the DI and AI? Did they just freak out every now and then, or were there just a bit off? I would agree with Airbedane though, best get it checked....
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Are you nuts?
This posting seriously bothers me! Whirlybird openly admits to flying an aircraft with suspect/defective instruments. Get a life fella and try to remember what AIRMANSHIP is all about. If you are an instructor, your students will be infected with your sloppy attitude. Dont need those instruments for VFR flight? In that case:
1: You dont need working flaps if it's a long runway
2: You dont need to secure loose articles if you're not doing aeros
3: You dont need any lights if it's daytime
4: You don't need to remove the control locks if you're only going
to do gentle turns
5: You don't need to carry a half-mil if you know the area
Dear God! They'll be issuing FI ratings to anyone with 2 forms of ID soon! bm
1: You dont need working flaps if it's a long runway
2: You dont need to secure loose articles if you're not doing aeros
3: You dont need any lights if it's daytime
4: You don't need to remove the control locks if you're only going
to do gentle turns
5: You don't need to carry a half-mil if you know the area
Dear God! They'll be issuing FI ratings to anyone with 2 forms of ID soon! bm
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Had a similar problem on one of our 152's this weekend. Answer was found in 2 places. The trim tab on the rudder had been bent out of shape and caused the aircraft to skid through the air. The second problem was loose screws on the instrument panel, the 150/152 left hand side panel is screwed in with all of the instruments, the screws had come loose while it had been sat outside in the bad weather and the vacuum pipes were dislodged causing a small air leak.
For those having a pop at whirly, if an FI was supposed to be the source of all knowledge including engineering where would there be a place for engineers? Genghis would have to take to posting on Pprune all day instead of doing any work..............
For those having a pop at whirly, if an FI was supposed to be the source of all knowledge including engineering where would there be a place for engineers? Genghis would have to take to posting on Pprune all day instead of doing any work..............
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Tee
Ref trim set as required, agreed it should be checked before takeoff.
Only excuses, I would expect a professional pilot to re trim for normal flight before returning the aircraft to base. The nose trim indicator on my aircraft can be apparently neutral,on the indicator, but have a strong out of trim rudder force, which makes retrimming while airborne not only preferrable,but also desirable.
Ref trim set as required, agreed it should be checked before takeoff.
Only excuses, I would expect a professional pilot to re trim for normal flight before returning the aircraft to base. The nose trim indicator on my aircraft can be apparently neutral,on the indicator, but have a strong out of trim rudder force, which makes retrimming while airborne not only preferrable,but also desirable.
Last edited by bluskis; 12th Apr 2004 at 09:57.
For those having a pop at whirly, if an FI was supposed to be the source of all knowledge including engineering where would there be a place for engineers? Genghis would have to take to posting on Pprune all day instead of doing any work
Back on topic, I did early on ask Whirly several questions; she's not answered them yet (probably still recovering) and a lot of people have made assumptions about the answers. Those questions were...
- Were vacuum indications normal ?
- Were there any airspeed problems?
- Did you really mean the slip-ball or the turn needle?
And another that's just occurred to me
- Apart from the normal wing points, at what points on the airframe was the aircraft tied down?
Whilst there's some good advice here, particularly from Airbedane and mad_jock (the latter is making assumptions about the answers to the above, but nonetheless I think is probably right), there are a lot of people making assumptions on incomplete evidence. Whilst that's the case, there will be plenty of work for both FIs and Engineers - of whatever variety.
Whilst waiting for Whirly to come back on those couple of points I'd make two points.
(1) Criticism has no place in this thread. Somebody has openly admitted to perhaps flying an aircraft that they shouldn't, and to not entirely understanding the problems. If we criticise anybody who has, after all brought the aircraft back in one piece, for being open about that then we've undermined the whole basis for aviation safety - at least in a civilised and (relatively) nonjudgmental country like the UK.
(2) I'd guess that most of us fly, or have flown, aircraft that are stored outdoors. Can we any of us put our hands on our hearts and say that every pre-flight has covered everything that either the weather or the passing public could possibly have done to that aircraft. I thought not!
G
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Genghis. Sensative aren't we........
I was only sticking up for whilrly and having a bit of fun with you. And anyway assuming you do the same amount of work as me is admitting that you generally do ****** all!!!!
I was only sticking up for whilrly and having a bit of fun with you. And anyway assuming you do the same amount of work as me is admitting that you generally do ****** all!!!!
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Well!!!!!!!!!!!!!!!!
I have a lie in, and come back to 14 posts, many of them very interesting. Thanks to...many of you. The others...need a reality check. Or maybe they're just dying to get a dig at me, given half a chance. Anyway, So now I know....
That many of you think that an instructor, ANY instructor, is supposed to be the source of ALL knowledge. Get real, guys!!!! We DON'T know everything. And that's not just me. I have always admitted to being weak on on technical subjects (though how dare you assume I don't know the DI and AI are gyro instruments, just because I didn't state it...I couldn't understand what the ball had to do with them though). If my students ask me about something I don't know, I tell them...and tell them where to find out. I'm sick and tired of getting jumped on for any question about anything I ask because I'm an instructor. I don't know everything. I have no intention of pretending to. Some of what I once knew I've forgotten. I'm a very new and low hours instructor. And I'm a human being, not a superwoman. Is that OK with you?
For the record, the suction indications were normal, as far as I remember...certainly before take-off. I checked the ball (yes, I mean the spirit level one) when taxiing, and knew it was well out; I said so in my original post. Nothing seemed to be bent (as I said), and it certainly felt as though she was flying in balance...or I would have returned to Sleap.
I thought the DI was erratic before I took off, though it worked fine when did the taxiing checks (and yes, I always do them). In fact, the DI and AI were erratic rather than non-working the whole time...and sometimes seemed fine, so it was confusing. As I said I'm happy using the compass (and don't you DARE ask if I know about compass errors!!!!), and I often prefer to - it means I can keep looking out of the window, and not look down at the panel. It's what I do in the R22, many of which don't have DIs. I consider a DI as definitely non-essential for VFR flight. Many of the R22s also don't have attitude indicators, so I'm used to flying without one. I consider that as non-essential for basic VFR flying too. There was no low cloud, just haze, and as an R22 pilot, I'm well used to NEVER going near a cloud. All the really essential instruments - compass, ASI, altimeter, VSI, were working...and I saw no reason why they shouldn't...the pitot/static system was working, and there seemed no reason why it shouldn't. I had a map. I had a radio, and a backup handheld one, and a working transponder. I had a working VOR, and GPS and spare batteries. And I was on a route I knew fairly well, with loads of diversion airfields if needed.
All those are why I judged it to be safe to continue. I felt the flight to be within my capabilities, after consideration, despite the suspect instruments. I OBJECT to the accusation of bad airmanship!!!!!! No, I wouldn't tell a student to continue under those circumstances. I am not a student. Perhaps there were indeed reasons why I should have aborted the flight. I did consider it. But having thought it through, I couldn't see any real danger, and I still don't. I could be wrong...but no-one's explained why yet. BoeingMEL, I suggest you learn to make considered judgements rather than merely following rules. Dear God, they'll be saying we should ground an aircraft with a non-working GPS or a loose ashtray catch next!!!!!
Airbedane, thankyou. Grounding the aircraft and getting it checked out definitely sounds like a good idea. Probably the best one given here. Since there is definitely a problem...and actually no concensus here as to what it is. And some of you expect me to know instantly just because I've done an instructors course!
bose-x, the loose instrument panel sounds like the reason for everything in that case. Probably caused by the aircraft shifting when tied down. That seems to make sense.
Genghis, there were no oddities in airspeed...or none that I could detect. As I said, she seemed to be flying really well (Cessna haters need not comment!). And I really checked that as far as I knew how, concerned in case I had an airframe problem and not just an instrument problem.
I hoped this might turn out to be an interesting thread, and it is.
I have a lie in, and come back to 14 posts, many of them very interesting. Thanks to...many of you. The others...need a reality check. Or maybe they're just dying to get a dig at me, given half a chance. Anyway, So now I know....
That many of you think that an instructor, ANY instructor, is supposed to be the source of ALL knowledge. Get real, guys!!!! We DON'T know everything. And that's not just me. I have always admitted to being weak on on technical subjects (though how dare you assume I don't know the DI and AI are gyro instruments, just because I didn't state it...I couldn't understand what the ball had to do with them though). If my students ask me about something I don't know, I tell them...and tell them where to find out. I'm sick and tired of getting jumped on for any question about anything I ask because I'm an instructor. I don't know everything. I have no intention of pretending to. Some of what I once knew I've forgotten. I'm a very new and low hours instructor. And I'm a human being, not a superwoman. Is that OK with you?
For the record, the suction indications were normal, as far as I remember...certainly before take-off. I checked the ball (yes, I mean the spirit level one) when taxiing, and knew it was well out; I said so in my original post. Nothing seemed to be bent (as I said), and it certainly felt as though she was flying in balance...or I would have returned to Sleap.
I thought the DI was erratic before I took off, though it worked fine when did the taxiing checks (and yes, I always do them). In fact, the DI and AI were erratic rather than non-working the whole time...and sometimes seemed fine, so it was confusing. As I said I'm happy using the compass (and don't you DARE ask if I know about compass errors!!!!), and I often prefer to - it means I can keep looking out of the window, and not look down at the panel. It's what I do in the R22, many of which don't have DIs. I consider a DI as definitely non-essential for VFR flight. Many of the R22s also don't have attitude indicators, so I'm used to flying without one. I consider that as non-essential for basic VFR flying too. There was no low cloud, just haze, and as an R22 pilot, I'm well used to NEVER going near a cloud. All the really essential instruments - compass, ASI, altimeter, VSI, were working...and I saw no reason why they shouldn't...the pitot/static system was working, and there seemed no reason why it shouldn't. I had a map. I had a radio, and a backup handheld one, and a working transponder. I had a working VOR, and GPS and spare batteries. And I was on a route I knew fairly well, with loads of diversion airfields if needed.
All those are why I judged it to be safe to continue. I felt the flight to be within my capabilities, after consideration, despite the suspect instruments. I OBJECT to the accusation of bad airmanship!!!!!! No, I wouldn't tell a student to continue under those circumstances. I am not a student. Perhaps there were indeed reasons why I should have aborted the flight. I did consider it. But having thought it through, I couldn't see any real danger, and I still don't. I could be wrong...but no-one's explained why yet. BoeingMEL, I suggest you learn to make considered judgements rather than merely following rules. Dear God, they'll be saying we should ground an aircraft with a non-working GPS or a loose ashtray catch next!!!!!
Airbedane, thankyou. Grounding the aircraft and getting it checked out definitely sounds like a good idea. Probably the best one given here. Since there is definitely a problem...and actually no concensus here as to what it is. And some of you expect me to know instantly just because I've done an instructors course!
bose-x, the loose instrument panel sounds like the reason for everything in that case. Probably caused by the aircraft shifting when tied down. That seems to make sense.
Genghis, there were no oddities in airspeed...or none that I could detect. As I said, she seemed to be flying really well (Cessna haters need not comment!). And I really checked that as far as I knew how, concerned in case I had an airframe problem and not just an instrument problem.
I hoped this might turn out to be an interesting thread, and it is.
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Bluskis
I agree with you that a professional pilot should re-set trim before returning the aircraft.
Genghis
There's more in this thread that 'undermines the basis of aviation safety' than the criticism it has attracted.
Finally, just for clarification, Whirly is a rotary instructor, not fixed wing
I agree with you that a professional pilot should re-set trim before returning the aircraft.
Genghis
There's more in this thread that 'undermines the basis of aviation safety' than the criticism it has attracted.
Finally, just for clarification, Whirly is a rotary instructor, not fixed wing