DI, AI, and balance ball all not working properly...Why???

[Whirlybird]

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! :eek: 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?

[Tee]

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??

[Genghis the Engineer]

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

[englishal]

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 :O

[paulo]

Parked on a sloping part of the field, near a giant high pressure air duct, a huuuuuge magnet (covering all bases here), and, erm, erm... :p

[Keef]

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?

[Islander Jock]

Balance ball a spirit level??! :bored: 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.

:p

[bluskis]

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.

[Mike Cross]

NOT a spirit level (hello, it's curved)
Suggest you take a closer look at a spirit level. The vial has curved walls, however the difference is that it is barrel shaped so it works in all planes. Essentially they work in exactly the same way, except in one the indicator is heaver than the fluid it sits in and in the other it is lighter. The glass ball in a liquid filled tube has better damping and is less affected by vibration.

Mike

[Airbedane]

Whirly - Ground your aeroplane and get a qualified aero-engineer to look at it before it flies again.

Then we can discuss what was 'wrong' with it.

Airbedane

[Tee]

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

[mad_jock]

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

[englishal]

Are we all carrying out proper checks before getting airborne and do we understand what the indications are telling us?
I'd hope anyone flying IFR would, however for VFR flight you could argue that its not nescessary.

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....

EA

[BoeingMEL]

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

[S-Works]

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..............:p

[bluskis]

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.

[Genghis the Engineer]

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

I should just like to point out that my average is 1½ posts a day (exactly the same as the poster of the above), so I do get some work done in between. Or at-least no less than bose-X



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

[S-Works]

Genghis. Sensative aren't we........:O

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!!!!

:p :p :p

[Whirlybird]

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. :ok:

[Tee]

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

[mad_jock]

Can you just clarify Whirly was it a Interior trim or where you talking about the trim wheel not being set neutral?

And to be honest I wouldn't have been bothered flying it VFR either if required for a positioning flight / test flight. I wouldn't except it for teaching though.


The vacum pressure indications really depend on where the leak is, where the suction gauge is and how good the pump is.

You can get sub normal rpms while still showing good suction.
I have had this and the only way i could tell was the DI felt soft when adjusting it.

MJ

[Genghis the Engineer]

assuming you do the same amount of work as me is admitting that you generally do ****** all!!!!

Damn, found out at last.:}




Well, offering an opinion now, the aircraft shifted on the ground, and the trim (which I understand to be the cockpit surround, nothing to do with pitch control) indicates that something's moved in that area.

Combining the normally reading ASI and Altimeter, with the poorly reading DI and AI, along with the knowledge that pitot-static hose is generally less stiff than vacuum system hose, suggests to me that the stiffer vacuum system hose, rather than the (usually) more flexible pitot-static hose (or possibly it's connections) has become damaged during it's shifting causing a partial or eratic loss of vacuum.

The damage must presumably be between the off-take for the vacuum indicator and the actual gyro instruments, since if it was nearer the vacuum pump then it would show as a suction failure. My best guess is that it's probably at the nipples on the reverse of either the DI or AI.

You've mentioned by the way that the AI has never been brilliant - it could be that this was the final straw in a progressive failure?



The slip ball, in my opinion, is probably the most difficult - a vacuum failure when flying VMC should be nothing more than an irritation once it's identified. The fact that somebody who knows the aircraft identifies no handling oddities, combined with the ball being similarly out on the ground would seem to eliminate a bent airframe (which if it's undercarriage would only show on the ground, and if it's wing would only show in the air - and both being bent to show the same errors without distortion being visible or any handling problems seems outside the realms of reasonable possibility). There is no external input into the slip-ball which can be distrupted. The instrument panel in a C150 is wall-to-wall so enough distortion to move a normal slip-ball out that much would, in my opinion, be readily visible.

So, my best guess is that the slip-ball has become damaged somewhere out of sight. If the case, this is probably the only thing to endanger the aircraft for VFR flight - not because it's an essential instrument, but because a fluid leak into the cockpit can potentially cause incapacitation.


So, my suggestion, following on from Airbedane's, is to have an instrument fitter remove the instrument panel and check all of the instrument connections (note ALL, something else may have worked loose but not shown itself yet), along with serviceability and alignment of the slip ball.

But, I would also have an LAME do a rigging check to be on the safe side - forces large enough to shift a large concrete block via the tie-down point may potentially have bent something that you don't know about yet. To be frank, at the wing/strut tiedown point on a C150 I think that it's unlikely, but it does no harm to check whilst it's in the hangar.

G

[ratsarrse]

because a fluid leak into the cockpit can potentially cause incapacitation.


Can you enlarge on this, Genghis? I would have thought that one of these slip ball things could only contain a small amount of fluid. Is the fluid really that stinky? Or maybe they're filled with a nice single malt...;)

[Tee]

How about-

(1) "Trim" (instrument panel surround) shifted because someone held onto it while pulling their seat forward

(2) Vacuum system failure which caused DI/AI problems

(3) Apparent problems with the balance ball caused by (i) flying in such a way as to compensate for the DI/turn indications, (ii) flying a fixed wing like a helicopter (ie too much on the feet) and (iii) flying on the compass rather than on the DI

[englishal]

The balance ball was out on the ground though.....

Could this be linked to the instrument rotating a few degrees in the panel, or the panel shifting slightly?

BoeingMEL, you should know (as a former professional pilot) that the minimum instrumentation for day VFR flight in a C152 is:-

ASI
ALT
Magnetic compass
Tacho
oil pressure guage
oil temp guage
fuel guage

Doesn't mention anything about any gyroscopic instrumentation.

EA

[Whirlybird]

To clarify...I was indeed talking about the instrument panel surround, not the trim wheel, which was just fine. Apologies for the ambiguity. I was tired, couldn't think of correct terminology, and didn't realise it was confusing.

Genghis,
Very helpful post. "Poorly reading" is the most accurate description for the AI and DI; neither had actually failed completely. So a partial loss of vaccuum makes sense.

The slip ball, in my opinion, is probably the most difficult - a vacuum failure when flying VMC should be nothing more than an irritation once it's identified. The fact that somebody who knows the aircraft identifies no handling oddities, combined with the ball being similarly out on the ground would seem to eliminate a bent airframe (which if it's undercarriage would only show on the ground, and if it's wing would only show in the air - and both being bent to show the same errors without distortion being visible or any handling problems seems outside the realms of reasonable possibility). There is no external input into the slip-ball which can be distrupted. The instrument panel in a C150 is wall-to-wall so enough distortion to move a normal slip-ball out that much would, in my opinion, be readily visible.

I couldn't have explained it in that much detail and that eloquently, but that was why I couldn't make any sense out of it. The ball was well over to the left, both on the ground and in the air. And the handling was definitely normal - believe me, with that many things going wrong, I was ready for anything, and checking everything at very frequent intervals. I too am wondering why a fluid leak into the cockpit should cause incapacitation, so please explain.

Tee,

How about-

(1) "Trim" (instrument panel surround) shifted because someone held onto it while pulling their seat forward

(2) Vacuum system failure which caused DI/AI problems

(3) Apparent problems with the balance ball caused by (i) flying in such a way as to compensate for the DI/turn indications, (ii) flying a fixed wing like a helicopter (ie too much on the feet) and (iii) flying on the compass rather than on the DI

Are you deliberately trying to wind me up? Because if so, you're going the right way about it.
1) Only two of us in the group, I'm the one who pulls the seat forward, and I don't hold on to the panel surround while doing so. OK, you weren't to know who flies the aircraft.
2) Agreed.
3) (i)The balance ball had identical problems while taxiing. I wasn't flying to compensate for the DI/turn indications; I was looking out the window and using the compass for...what it's there for! I don't find a lack of DI and AI a major problem requiring any change in the way I fly, merely an irritation.
(ii) Actually, in a helicopter you hardly use the pedals in the air, only while climbing, descending, or especially while hovering. And I DON'T fly a C150 like a helicopter!!!!! And like I said, in very light wind, she was flying beautifully hands (and feet) off. (iii) There is absolutely nothing wrong with flying on the compass rather than the DI in VMC. As I said, I do it frequently, so that I can keep looking outside rather than at the instrument panel. It really worries me if people think using the compass for navigation is something odd, difficult, or likely to cause errors; it isn't. In some ways I actually prefer a nav instrument that I don't have to keep adjusting...though if I have a working DI I do set it and tend to use both of them. If PPLs are ending up thinking using the compass for what it's designed for is somehow odd, I can think of some criticisms to be levelled at other instructors!!!

Anyway, we'll definitely get things checked out before she's flown again. Thanks people. :ok:

[Chilli Monster]

Boeing MEL - what b:mad:s!

Having had (yesterday) a complete vacuum failure half way along the first leg of a 3 part cross-country then I have to ask - what's the problem? (and this was San Francisco - Long Beach via two intermediate stops, not some little UK tootle). Weather was VMC on top during the failure with a a VFR approach, the subsequent ones were flown VFR. Flew the aircraft by compass, turn and slip, and VOR (Seneca in this case). The most important piece of eqpt. required was the 'post-its' to cover up the faulty pair!

Maybe your comments underly a personal worry that partial panel would be too difficult?

Whirly

Can't add anything different to what others have said. However, I would re-iterate checking the mounting of the turn co-ord (a la EA's answer). If the aircraft trims straight and level still then it's probably just this coupled with suction problems.

[FireDragon]

Whirlybird

If you can't post properly when you're tired, DON'T post until you're awake...

[Keef]

Whirly, post whenever you like. The adults can handle it.

If the vacuum gauge (not guage) is showing around 5, then there's no leak. It's more likely to be blocked or "old" filters, or (less likely) kinked tubes to the instrument that's messing around.

Be interested to know the diagnosis (if there is one, rather than lots of messing around behind the panel, during which the problem miraculously disappears).

[Genghis the Engineer]

The following is taken verbatim from the Winter 2000 issue of CHIRP GA feedback, which is online at http://www.chirp.co.uk/new/Aviation/IndexAir.html

I know of no particular differences between the fluids in compasses and slip-balls, and hopefully justifies my comments about incapacitation.

G


Pilot Incapacitation

Reported occurrences of pilot incapacitation in General Aviation are relatively rare, but that does not mean that the problem does not exist. Incapacitation can result from several causes and may have extremely serious consequences in a single-pilot operation, particularly if the problem is not recognised at an early stage. The following report describes the insidious nature of some forms of contamination and the benefit in taking prompt action.

I collected our group PA32 from the Midlands on a Spring morning in 1994 for a day trip, with my wife and small children, to visit relations near the South Coast. On checking the aircraft I examined the 'snag' sheet, which was used to detail any known faults/comments noted by previous pilots and still outstanding. A 'snag' had been noted that stated that the compass fluid was leaking. Inspection of the compass (top centre on the windscreen) showed a small bubble at the top. Conditions were good VMC, the VORs all worked correctly, I was familiar with the route and I also carried a small hand compass in my flight bag. I could check the Direction Indicator against the runway heading prior to departure and with the aid of VORs in flight, so I was quite happy to go ahead.

On climb out I did notice that a prolonged trickle of fluid ran from the compass onto the carpet just in front, and between, the pilot and front passenger seat. I thought nothing more of it. After about 20 minutes my wife complained of feeling sick - very unusual, as she has never experienced airsickness. However, it was a little bumpy so, again, I was not unduly concerned - although I did register the fact that the compass fluid did produce quite a strong smell. A few minutes later she was clearly in some discomfort, shortly followed by a complaint that she was losing the feeling in her legs. She does suffer from mild asthma and it then struck me that she could be suffering from the affect of the smell of the fluid leaking from the compass. I felt fine but, as a precaution, I immediately adjusted all the available fresh air direct to my face. I then diverted to the nearest available airfield and executed what I thought to be a perfect landing just 10 minutes later - only to be told as I turned off the grass runway that I had landed "off the runway". I had, in fact, not noticed that the runway markers had recently been moved and, instead of landing between the markers, I had landed on the nicely cut strip to the right of the right side markers. I still felt fine - although slightly embarrassed!

On explaining my predicament as I taxied to park the aircraft, the airfield could not have been more helpful, instructing me to immediately shut down. They entertained my children, provided first aid for my wife who rapidly recovered in the fresh air, and removed the compass, which we carried home in the external locker - all without charge or landing fee! After an hour or so we completed our journey.

It may be just as well that my wife's asthma probably caused her to be more sensitive to the smell giving me advance warning of the problem - the prospect of heading west on autopilot whilst slowly losing one's judgement does not bear thinking about! I certainly do not recall any aspect of my training (including commercial balloon pilot exams.) that warned of the dangers of noxious fumes from a leaking compass!

[Whirlybird]

Just been talking to the other group member, now back after Easter. Aircraft will hopefully be looked at in the next couple of days. I'll let you know the diagnosis.

We're also looking for a better place to tie her down.

I'll continue to post, tired or not. Of course I will - I'm a PPRuNe addict. Most people seem to understand what I say. the others will just have to put up with it...or not bother reading. :D

Again, thanks for all the useful comments.

[BoeingMEL]

Mmmm a bit of a hornet's nest here methinks! I make just 2 more points here and will then retire with a cold beer.

1: Airmanship encompasses more than the carriage of minimum equipment.

2: To suggest flying partial panel with all gyro-instruments out in VMC may not be a problem. Now try the same exercise if the vis deteriorates or with your windshield coated with several litres of hot engine oil.

In this old-timer's experience, the pilots who are sloppy about planning, preparation and safety are usually the ones who cant get close to +/- 50', 5 degrees or 10 knots..... cheers! bm

[Whirlybird]

Ah, BoeingMEL, I had a look at your profile. Fly the 737 and B206 do you? That explains it. You're used to lots of instruments. But to me, you see, this wasn't partial panel; it was what I'm used to anyway. Along with most pilots of cubs, austers, microlights, and a whole collection of other aircraft. The DI and AI were useful luxuries. Must admit though, non-working instruments are distracting; Chilli Monster's post-it notes would have been useful.

Deteriorating vis? I'd divert - loads of airfields on that route. I'd do that anyway, since I don't hold an IMC. Several litres of engine oil!!!! Possible but unlikely. OK, I admit it; I hadn't thought of that one!!!

Planning and preparation done in detail. Checks done, go/no go decision considered in detail. 50', 5 degrees, 10 knots...the limits for the CPL(H) flight test, which I passed on an R22, one of the most unstable flying machines there is...much much MUCH easier in a C150.

Hmmm...Whirly, he obviously isn't even discussing you; why are you even posting? :confused:

[Genghis the Engineer]

She's right you know Boeing.

There is nothing wrong with flying a simple slow aircraft like a C150 with a faulty vacuum system, nor without a serviceable slip-ball so long as you know that those are faulty, and nothing else is .

I've flown, quite legally and safely, aircraft who were equipped with an ASI, altimeter and compass, and nothing else (and two of those were not part of the MEL). They were, to be fair, types that maked a C150 look complex and high-performance, but they were still aeroplanes. Conversely, you'd not fly your 737 with the standard C150 instrument fit would you. It's all horses for courses.

I still stand by my concerns about a possible leaky slip-ball mind you, but it would appear from responses above that nobody else, however experienced, was aware of that PA32 report and it's near-nasty consequences - so if nobody else was, it's a little hard to criticise Whirly for lack of awareness on that point.

G

[S-Works]

I have to say BoingMEL I agree with Whirly here. I also fly microlights as well as significantly bigger stuff and Rotary.

The microlights I fly have no gyroscopic instruments at all, in fact all they have is an altimeter, VSI, compass and RPM guage and so find your insinuation that a pilot who flies without them is sloppy a little offensive. I certainly find no problem with speed/height/heading during CPL/IR ops or flying an aircraft with minimal equipment VFR. There are also a lot of other Microlight and classic aircraft pilots out there who seem to back this up with safe flying?

Perhaps you have become too reliant on technology and this has clouded your view of the simpler things?

I had an an engine blow oil onto the windscreen in a microlight about 15 secs before it stopped. I put my head out the window and landed safely. No need for any gyro instruments there.

If you are in a 152, you have inadvertantly entered IMC and then the donk quits and blows oil over the screen it probably means your going to have a bad day. Not sure how a fulll set of gyros is going to help in that situation!!!

[Evo]

Genghis - I know (well, third-hand) of two pilots who were recently made to feel very unwell by a leaking compass; like others here, I was surprised that it could have such an effect.

[Genghis the Engineer]

If the donk quits in a 152, you don't have any gyro instruments anyway - they're driven by an engine Vacuum pump.

G

[BoeingMEL]

Healthy debate and enjoyable too! These exchanges of opinion exercise the grey cells and do extend knowledge and understanding! Just to make clear though.... when "my" Bonanza dumped oil over the windshield, the donk didn't quit... the guage still showed 30 psi when I landed 15 minutes later (after an ILS approach to minimums and landing looking through the side window.) Secondly.... and I do believe this passionately: any PPL instructor can (and should!) learn about those instruments and be able to describe their operation clearly to students. Dear God.. there cant be more than 3 or 4 hours learning to cover them all! Kind regards to all bm

[FlyingForFun]

Whirly, I have no idea what could cause the balance ball to fail, so I won't even try to add to the excellent-sounding answers from those who know!

But I will add to the debate about flying without these instruments. I agree with you - not a problem at all!

On my 170A flight for my CPL, I had a genuine vacuum failure. Was approaching a turning point on the navigation section of the flight when I glanced down at the instruments prior to making the turn. Was quite surprised to see the AI pointing off in some obscure direction. I checked the cockpit and quickly realised that I'd had a vacuum failure. My instructor was sitting there quietly, and although I wasn't aware of any way of disabling the vacuum system from inside the cockpit I suspected that this was an instructor-induced failure. I told my instructor what I was doing, made the turn on the compass, and expected the instructor to restore the vacuum, but no - this was a genuine failure.

We completed the flight without any further incidents. (The b@stard instructor still put me under the foggles for the diversion and had me do the entire instrument section of the flight partial-panel, too!) During the debrief, instructor told me that he'd noticed the failure a good 5 minutes or so before me. So it seems that it's quite possible to fly an aircraft without looking at the instruments after all ;)

FFF
---------------

[White Shadow]

Horses for courses. Yes, indeed.

I tried out an expensive hot-ship microlight recently.
To save weight, instrumentation was a liquid-crystal display, with a row of buttons to bring up whatever particular info you decided you wanted -

Analogue ASI; analogue VSI (both single-pointer or sector-arc display)
Digital Altimeter (buttons to set QFE/QNH); Digital tacho.
Plus a whole lot of other stuff like CHT, EGT, Fuel consumption l/hr, fuel contents (which you had to set zero at the quantity you had in to start with, then read according to what the consupmtion-monitor calculated you'd used since you started). Clock (real-time/elapsed-time). Voltmeter. Flight data recorder. Outside air temp. etc etc.
You get the idea. Clever stuff.

Anyway. trying to pin revs & trim for S&L at the airspeed I wanted, or the ROC/descent, was interesting, to say the least.
The CFI, who was introducing me to this very pretty, sleek, fast aircraft said
"Oh, forget thet lot. Just FLY the thing"

WS

[mad_jock]

BoeingMEL yes I agree and most should be able to spurt out the standard blurb about how they work aka ATPL theory.

But trouble shooting a knackard plane is an art in itself. Just watch the engineers run for cover when they know there is an electrical fault coming in. I have it on reliable info from a licensed engineer the best method of starting on an intermitant electrical problem is to sacrifice a chicken to the dawning sun. Then if you can't fix it after a day a FI to the setting sun ;)

And the bloody machines never fail the way the book says. Thankgod the donk is the most reliable bit of kit fitted to the aircraft. With the clock being the least reliable :D

As said previously the FIC doesn't prepare you for even half of your job as an instructor all the rest is learnt on the job. If you have a technical background you have a huge advantage. But if you have a degree in media studys you don't really have much to work with apart from of course your people skills (And what ever you learned in Burger King). Which have yet to fix a plane when its knackard (unless of course your a large breasted blond 25 year old female FI who has every engineer in a 50 Nm radius wrapped round your finger).

Unfortunatly whirly is short and err middle aged enough to be my mother, and i might add just as lovely as my mum. Who's lack of troubleshooting skills on sick aircraft (fixed wing) which are more than made up by her understanding and human skills working as an instructor on rotary.

MJ

[paulo]

Any news whirly? I'm quite curious - about the balance ball more than anything else.

[2Donkeys]

The balance ball is the most interesting feature of all. The gyro instruments can be explained by a variety of factors, most if not all of which have been aired on this thread.

A significantly displaced balance ball whilst on the ground suggests things like big shifts in the instrument panel mountings or deformation of the airframe, landing gear, tyres or similar.

All other comments notwithstanding, it was not a great idea to take off with an unexplained defect of that sort.

Hope it all works out well, I wait with interest to see the "proper" diagnosis.

2D

[Whirlybird]

paulo,

Hoping to find out myself soon, and I'll post here when I do.

[Miserlou]

My initial thoughts are that there's nought wrong with the slip ball and that the apparent errors are the turn on the DI due to the rudder input or lack of (to keep the ball centered) and the slight bank on the AI required to fly level with the slip.

As my old Dad used to say, "Problem is the nut that holds the wheel!"

Interested to hear verdict.

[2Donkeys]

Miserlou

You are perhaps forgetting that the balance ball was judged to be "well out" whilst on the ground.

[Whirlybird]

The other group member says it doesn't make sense. The aircraft is designed to survive heavy landings etc, certainly more than a heavy gust of wind. This is true. However...

We can't lock her, and it she is tied down in a very quiet area of the airfield. He reckons someone has been swopping instruments!!! :eek: :eek: :eek: Frankly I think that's a bit farfetched, but it's as likely as anything else. And the slip ball was right out to the side, both on the ground and in the air; we're not talking about a slight inaccuracy here.

Anyway, she's being looked at on Tuesday. Till then, I think any more speculation is a bit pointless. I'll let you all know the verdict.

[Miserlou]

I may well be forgetting about it being out on the ground too but...

Whatever position it is in when the aircraft is stationary on level ground is the straight and level position in the air. If it doesn't react when turning on the ground then its stuck; lack of spirit perhaps as mentioned earlier. I thought it was a sealed vial.

[Whirlybird]

Two of the instrument panel mounts have sheared off. We think they were worn anyway, and when she shifted in the gale that did it. If you hold the panel straight, the ball goes back to the centre. There appears to be nothing wrong with the AI or DI or any vacuum problem, and the poor performance was probably caused by vibration. We won't know that for certain till the engineer checks it and replaces the mounts, which are on order. I told him I hoped to fly it at the weekend, and he said it should be OK by then.

We begged for a better place to tie her down, and now have it...hooks cemented into the ground to tie her to. We spent the afternoon sorting all this lot out, and cleaning and polishing her. Just about all we didn't get to do was fly - that comes next weekend.

Thanks for all the comments, and I can't remember who gets the prize for guessing correctly, but I think someone did. :ok:

[S-Works]

That will be me then......... :O

[paulo]

certainly wasn't me. :)

[Gertrude the Wombat]

During the debrief, instructor told me that he'd noticed the failure a good 5 minutes or so before me. Well, yes, he would say that, wouldn't he :)