Dafydd Llewellyn

I'd not tackle anything major on a Jab OR a 912; though I've fully rebuilt many a car or light truck engine; there are too many subtle little tricks and special tools involved.

 

 

Nev, you're a comfort. My kids were allowed to use the car (on our 5-acre block, west of Sydney) to take the rubbish to the incinerator, which was a couple of hundred yards from the house - only in first gear - as soon as they could fully depress the pedals. They could do 3 - point turns with a trailer, by the time they were fourteen. I put both of then through to solo in gliders before they were allowed to take the car on the road, so they got the feel of being responsible for their own lives, in a disciplined environment; and I taught them to analyse what the driver in the car is front was thinking, by the way he drove - and to generally drive "ahead" of the vehicle. We moved to QLD when the younger one was seventeen; purchased a 1 1/2 ton Nissan light truck & built a pantechnicon on it, and it took 28 round trips to move our stuff to QLD; they each did a couple of trips as co-driver with either me or my wife, then we took it in turns. They were both very competent, but I didn't know about that risk processing thing Vs age, of course. They didn't scratch the truck; and you certainly had to drive well ahead of it in places like Moonbi and Murrurrundi Gap. It worked for the elder boy, but not for the younger; he had a very serious accident at 18 and later wrote off several vehicles through going to sleep at the wheel - didn't seem able to know when to stop.

 

Nowadays, we're both in our '70s; my wife owns the Blanik, and is the maintenance controller. She has about 60 hours in gliders and a restricted PPL; she's currently at Keepit doing a refresher course, because it's been a while since she did any flying; and I'm the GFA inspector. The Blanik is full dual control, with dual instrument panels, including the engine instruments and control of the VHF COM, and we will alternate as to who is in which seat, just as we do in cross-country car trips. The one in back navigates with paper, and manages the refreshments; the one in front uses the ipad. So we'll be flying as long as we're physically fit.

 

 

Dafydd, as I recall you told us you certified this engine. You used the quaint "certificated" term , but when you certify something for the automotive arm of the Department of Infrastructure and Regional Development you have ownership in that product.It's not product liability you need to be worried about, it's public liability, and if someone doesn't make it in a forced landing the lawyers decide who they'll go after.

 

So it would be in your interest to answer either directly or by example, Motz's question. Your comment above is not a good look.

You recall incorrectly. And the legal term is "certificated" (i.e. issued with a certificate); look up the regulations. If you do not comprehend that there is a difference between CASA and the automotive arm of the Department of Infrastructure and Regional Development, it's about time you did.

The Jabiru 2200 J and 2200C were certificated by CASA; see for example http://www.casa.gov.au/wcmswr/_assets/main/casadata/cota/download/ve501.pdf

 

Nobody but CASA has the authority to issue a Type Certificate. I was involved in quite a few of the aspects of the type certification testing of the Jab 2200J; but I did not do any of the finding of compliance.

 

The Type Certificate is a certification BY CASA that the product complies with a specific design standard (product safety standard). I strongly suggest you read CASR 21 subpart B before you make this sort of pronouncement.

 

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

I have no commercial interest in Jabiru or anything Jabiru does, and no say whatever in the management of the company; I've simply been used by them as a consultant from time to time - mainly in regard to flight testing, but also in helping to run the J2200 engine certification tests. Those tests were run under the observation of about half a dozen CASA engineers, who were on-site for about a week.

 

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

 

This is what annoys me.. Why should it be up to Ian, or camit, or the owner to sort the problem?

Good question. Next question?

 

 

spend time looking at the task of allowing those who engineer upgrades be allowed to implement them. Start investing time sorting out regulatory ways out for all those stranded and broke Jabiru owners mentioned. Running down the product and belting on about Jabiru fixing it, isnt working and is unlikely to. Just brings down Jabiru owners not the company.Just say we follow your advice, totally redesign engine (to you specs of course) and it without doubt proves to be reliable for 5000 hrs TBO without even oil changes. How is this going to help 25 reg Jabiru owners?

 

Jabiru either cant or wont get involved in re-engineering their engines. Maybe from experience in things like Hydraulic lifters. Where what was a widely used and promoted technique has turned out to be a major contributor to a string of problems over years. No doubt cost them dearly and IMO still does. Continually saying that they should fix it is such a waste of time.

 

Now with Ian working on his own thing I doubt he is going to hand his IP to Jabiru. Leaves them with problems and not much solution.

 

People with LSA purchased them with the restrictions in place to get a factory built aircraft. It was always going to be the case that were there issues builder wouldn't recognize, see a commercial conflict etc etc. that they were stuck with what they bought. Even common sense upgrades would maybe not be permitted.

 

Aftermarket upgrades is a logical and solid answer but at this stage they can only sell them to small number of 19 regd aircraft so who would spend the time and money? And it will take a lot of both.

 

How about get going getting paperwork together on 912 transplants going, build a kit.

It doesn't need a "Committee to re-invent the Wheel"; the regulatory options are all set out in CASR Part 21.

IMHO, LSA is a dead-end, for the reasons JJ has mentioned. The "Solid" way is via Supplemental Type Certificate modifications (CASR 21 subpart E). You have only to look at the plethora of STCs approved by the FAA to see how important this mechanism is; but it's not available for LSA aircraft.

 

 

I've no issue with people reporting problems - that's certainly what a forum like this is for.

 

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

The best way to help existing Jab owners is to provide an engine rebuilding service that deals with such issues as Ian Bent has identified; that's what Maj evidently saw (and did not comprehend). The advantage of doing it that way is that there would be no legal hoops to jump through about putting it into an existing airframe, because it's legally a Jab engine with approved modifications.

 

Of course it still looks like a Jab engine; it still IS legally a jab engine, however the product liability would be divided between CAMit and Jabiru in some way according to the modifications, and that may well be a bone of contention between CAMit and Jabiru.

 

If that approach is blocked by the product liability issue, then the alternative will be for CAMit to go the whole nine yards, and certificate an engine containing the lessons from the Jab engine, plus a few more fundamental changes. That would probably produce a better engine still, but it then involves an STC to put it into certificated airframes; and it would still need Jabiru's "No objection" response to put it into LSA airframes.

 

So, where to from here? That depends on some resolution of the product liability issue; and some other commercial aspects on which I cannot comment. But sniping at Ian Bent's attempts to come up with an overhaul program for existing jab engines to incorporates improvements - many of them too subtle to be obvious - for what would remain fundamentally a Jabiru engine - on the basis of "that's not the way Grandad did it" (or any other similar bar-room wisdom), is not helpful.

 

 

More than happy to Nev, in fact I have been saying this for years now with nobody really listening. I feel the very basis of all the jab problems lies in the CNC machined- from -billet engine case, and I don't feel the problems will ever be solved ( by Camit or anyone) until such time as they change to either a cast or forged alloy case like everybody else uses. The only other engine block I know of which was CNC machined billet wa a drag race engine called a Donovan.It was an exact copy ( with some improvements) to replace the old chrysler 'elephant' cast iron blocks which became hard to get. The Donovan wa only intended to be used for a couple of runs, and I don't even know if they still use them or not.

 

When you CNC mill something out of solid billet you release a lot of internal stresses which wants to throw the finished machine tolerances way out of wack. Unless you intimately measured every dimension on each billet case ( and there would be many to accuratly measure) and rejected those cases that were beyond tolerance, your basically getting what you get, and we've seen the results of that.

 

Additionally a billeted case with a rotating steel hot crankshaft within trying to escape, and very hot steel cylinders attached to it is thermally unstable at best. Your asking for hot spots. The alum wants to move around and expand way more than the steel, hence why they break cylinder and case studs all the time.. Lets remember even the new upgraded ones are still breaking, and there's only one common denominator ...the alum billet cases. Same with the billet heads...not thermally stable enough. Lets get to the valves now, their design is archaic at best. They didn't 't even have oil supply galleries in their valve guides until recently, critical to keeping an exhaust valve cool and eliminating excessive wear on bronze valve guides. Exhaust valve seats set in billet aluminium will not stay there...once again the thermal expansion thing between steel and aluminium ..and for them to have half a chance the valve clearance is absolutly crucial ...too tight with no clearance and its all over red rover very quickly with the valve seat.

 

And if all this is no enough let get to the oil cooling situation on the Jab....ah ....second thoughts, let's not !......I mean what other engine have you ever come across where you have to consult the operators manual to get your proper oil level on the dipstick for your particular engine !....and then have to be happy with 1/8" of oil on the end of the dipstick !...come on now.

 

And Camit ?........looked over their 'new' case at Natfly last,.....same billeted case to me.....oh and what's all these funny oil lines running all over the place?...........oh they are so you can squirt a little oil into the cylinder so the barrels won 't rust when your done flying, replied the friendly sales lady ....give me a break darling, why don't you use high grade carbon or chromium steel like everybody else for your cylinders, and the damn things won't rust in 50 years.............!!!.. So what the magic answer in my opinion ?....go to a cast or forged alloy case like Lycoming, Continental, Pratt & Whitney and Rotax have used for years, and I reckon reliability will improve overnight. Thanks for asking..........

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

Point 1:

 

Lycoming and Continental crankcases are made from 355 alloy, which is an aluminium/copper alloy. It starts out in the -T6 heat-treat condition; but it slowly loses strength due to the operating temperature. How do I know? Because I approved a new weld repair process for those crankcases (after a lot of research, done by Rudi's Aero Engines, in conjunction with my son Bob, who was acting as my junior engineer at that time. It took a lot of testing to convince CASA). They usually need weld repair sometime during the second engine life; and by about half way through their third life, they are down to close to dead soft, with weld repairs all over the place, and should really be scrapped. Those cases are sand-cast, NOT forged. They are heat-treated after casting and before machining; thus they have locked-in stresses that may be released during machining, too.

 

The principal problem with cast crankcases is porosity; however a billet case uses wrought material, which eliminates the porosity. There is no wrought equivalent of 355; so Jabiru used what they could get, i.e. 5083. I've not heard of Jabiru crankcases cracking in service, tho no doubt they would if they were run long enough; the principal service problem seems to be indentation of the cylinder flange seat, due to flexure of the "ears" of the cylinder flange, which contributes to(but is not the sole cause of) the loss in through-bolt pre-load. That's not a crankcase design issue; it's a cylinder design issue, which CAMIT has addressed. The Jab. crankcase does not normally get sufficiently hot for thermal instability to be an issue; and it does not start out in a high heat-treat condition.

 

CAMIT have extremely accurate measuring apparatus which runs continuous sample checking, under computer control, so it's not fussy how many dimensions it has to check.

 

Point 2:

 

Jabiru cylinders are machined from 4140 steel, which is a high-grade chrome-molybdenum steel containing 0.4% carbon. In what way does this differ from the material used in Lycoming cylinders? 4140 can be nitrided, as are Lycoming cylinders; however the Lycoming 0-320-E2A engine used in early PA 28-140s had non-nitrided cylinders, being intended for flying school use. I had one; it retained excellent compression right to the end of its overhaul life - but I made a point of doing a couple of circuits in it at least once a week, as recommended by Lycoming. Lycoming cylinders, including the nitrided ones, ARE prone to corrosion unless they are in frequent use; they used to sell chrome-plated cylinders for private-owner aircraft that did not get regular and frequent use; however they've stopped doing that.

 

The crankcase is, unfortunately, NOT the only common denominator in the through-bolt saga.

 

CAMit are focussing on solid-lifters because the routine checking of valve clearances is the best way of monitoring cylinder head and valve issues.

 

 

For what it's worth - aircraft that need to be able to fly slowly - which includes all ultralights that have a restricted stall speed, and gliders, which have to be able to turn with a small radius of turn, to stay in a thermal - have highly cambered wings. A highly cambered wing wants to turn nose-down - in technical terms, it has a negative pitching moment. That pitching moment increases in proportion to the square of the speed; so the download on the tail to balance it also increases in proportion to the square of the speed, which generates considerable structural loads. The tail load also increases the tail induced drag, and since the wing has to carry the tail load as well as the weight, it increases the wing induced drag a bit, too.

 

If the wing uses a laminar-flow airfoil (as gliders do), there is a second effect; laminar airfoils have a reduced drag over a limited range of angle of attack; this is sometimes referred to as the low-drag "bucket" because of the shape of the lift/drag curve. Outside that "bucket", laminar airfoils usually have a higher drag than the conventional airfoil on the jabiru etc. Reflexing the trailing-edge surfaces moves the low-drag bucket, and can therefore increase the usable speed range in which low drag occurs.

 

Both these things can be a reason for the designer to use "variable camber" via symmetrical movement of the flaps and ailerons. Doing so helps keep the fuselage close to its minimum-drag angle. However, the total performance gain is relatively small - and it greatly complicates the task of certification, because all possible geometries have to be investigated.

 

An example of this was the Pik-20B glider, which had a crank-handle on the left of the cockpit to change the wing camber. The sensation that gave the pilot was spectacular - on leaving a thermal, one did not shove the stick forward to gain speed, one wound the crank, and the airspeed shot up with no perceptible change in attitude - it was almost as though you were cranking the ASI needle around the dial. However, the actual performance was really much the same as its contemporaries without this feature; it just felt faster. Most current gliders use it, to squeeze the last bit of performance - tho I wonder whether it's more a case of squeezing the last dollar from the consumers.

 

 

Earhart's aeroplane was a Lockheed 10; same No. of wing, engines, and tails as a Hudson, but certainly not the same airframe.

 

 

See australian standard as/nzs 2906 - fuel containers - portable - plastics and metal - it does not appear to address electrical conductivity.

 

 

I've used plastic funnels to refuel various pieces of machinery around the place, and I've been lucky, too. I suspect there are two mitigating circumstances - firstly, the flow rate is small (and so is the total quantity of fuel). Secondly, there's a rather over-rich fuel vapour/air ratio in the area where sparking is most likely. But on the other hand, I've seen several hideously-burned acquaintances over the years - so it does occasionally happen. I suspect you will find that the Australian Standard for plastic fuel containers may specify a minimum conductivity; and maybe an intelligent maker of fuel funnels would use the same material - but that's a guess.

 

I think the aviation requirements for refuelling aircraft are the result of WW 2 experience; putting a couple of thousand gallons into a Lancaster or whatever in a hurry, is far more likely to build up a dangerous static charge, than pouring 40 litres into an ultralight. However, stainless steel hardware is much easier to get, nowadays, and it's cheap insurance.

 

 

How about ensuring that the aircraft is correctly earthed before refuelling; or am I missing something here? Are the plastic tanks the issue?

I think it's more important to ground the aircraft to the refuelling equipment; however grounding that to Earth would seem cheap insurance. Bit of a challenge to do that for a mobile refuelling rig, though; you plan to drive a metre-long copper-plated steel rod into the ground to serve as an earthing electrode? Don't let the groundsman spot you doing this . . .

 

 

Getting back to the question of why were some manufacturers or aircraft disallowed (for want of a better word), the answer may be found in CASR Part 21.186.1(a) and CASA AC 21.42 - in particular, the latter, which explains what it takes to become a manufacturer of LSA aircraft. Amongst other things, the manufacturer needs to either (1) hold a Production Certificate for an aircraft of comparable complexity, OR (2) must have the services of professional persons acceptable to CASA.

 

See http://www.casa.gov.au/wcmswr/_assets/main/rules/1998casr/021/021c42.pdf

 

 

I use a metal drum on wheels with a rotary hand pump, there is a filter and a fuel hose with a metal nozzle and an earth wire from the drum to the aircraft.

I used to refuel my Auster - which I used to fly to & from work at Hawker de Havilland at Bankstown, in the '60s - from a metal drum (half a -44) in the boot of my car, with an all-metal hand pump, a metal-mesh filter, and the hose had a steel spring inside it, in contact with the fuel; plus I had an earthing wire from the set-up in the boot, to the aircraft. The only problem I had was that the pump and the spring inside the hose were not made from stainless, so they rusted, and of course so did the drum - and though the filter caught the rust particles from the pump, the ones from the hose made it into the aircraft fuel system (where they were caught by the gascolator). It's not difficult to get stainless steel mesh that will stop water; and this is a much safer option than using a chamois, and plastic funnels etc are simply asking for trouble.

Pick your hardware with care for these issues, and you can make a very satisfactory refuelling rig, for no great cost. But don't use galvanised steel; use stainless, or if you can weld it, aluminium for the non-wearing parts. A time-ex LPG tank from a car makes a good basis. However, it's probably illegal to do such things these days, except on your own property.

 

 

You are entitled to your opinion. I'm simply pointing out the requirements of the design standard to which the J 160 was certificated. If somebody wants to re-paint one of those, that's a modification and it requires approval - and approval requires compliance with the design standard. Go argue the toss with Darren Barnfield.

 

 

funny how heat absorbency doesn't seam to effect military aircraft, or any other civillian aircraft for that matter, even in desert environments of the Middle east.. and yes, im referring to composite structures.. and no, in my 25 yrs in aircraft composites, have i ever seen 1 incidence of delamination or damage due to black, or matt black painted composite aircraft or parts sitting in the sun..

Nothing funny about it at all - that's because the composites in those aircraft are generally made with pre-preg, and cured in an autoclave - whereas Jabiru use hand layup, ambient temperature cure. Pre-preg stuff comes out like bone china - and it's about as brittle as that, too. Ideal for short-life aircraft where performance is more important that anything else.

 

 

Not as far as I am aware - and the design standard makes no allowance for that.

 

 

I believe I read somewhere that the impact of the ambient temp was more an issue when the resin was new and as it aged the risk reduced......I cant remember if or what science was presented to support that point....Andy

The Tg can be increased by curing the resin at an elevated temperature, depending on the resin. The scope for this is pretty limited for LC 3600. Jabirus - at least the models I'm familiar with - are not cured at elevated temperature, because doing so also makes the resin more brittle; they do cure progressively by natural ageing, so the Tg will increase as the aircraft matures - but not indefinitely, and the process is not quantifiable. Alan Kerr was of the view (based on numerous tests) that this practice considerably increases the fatigue resistance of the layup, and also its impact resistance; some of Jabiru's crashworthiness is likely due to this. I am not aware of any research done by the African or American vendors to justify darker colours, tho presumably they have some experience by now.

The weave becoming visible is a consequence of long-term resin shrinkage and is a characteristic of GRP in general; it is usually disguised by including a layer of surface tissue on the outer surface of the layup, but that adds considerable weight, so it's a luxury small aircraft cannot usually afford.

 

 

Fully aware of this thanks dafydd, you can see the weave coming to the top on some jabs that have been painted, by paint scheme I assumed it would be understood as the stick on graphic schemes. Interestingly the Jabirus being sold in America and South Africa have near full paint schemes not stick on's. I was thinking of covering the belly, so you think there would be much reflected heat from the ground?

The Tg (glass transition temperature) issue is the temperature the thing gets to, standing in the sun. I doubt it matters whether the colour is painted on or stuck on. I can only suggest putting some temperature sensors on the top & the underside, parking the aircraft in the full sun, and recording the temperatures over a reasonable range of sun angles. Here's the part of AMC VLA 613 c that I couldn't attach last night:

 

 

Interesting point - what about dark colour schemes applied to aluminium? Would there be any difference (stretching, wrinkling etc) depending on colour? I know Zenith painted a few of their demonstrator models dark blue.

No; you can paint aluminium any colour you like.

 

 

The Jab is white for a reason. Ever hear the term "glass transition temperature" for an epoxy resin laminate? I suggest you look it up, before you add much in the way of a colour scheme. The Jab is made using LC3600 resin. The structural testing was conducted at or slightly above 54 C, because that's the temperature considered necessary for a white-painted surface in full sunlight on a nominal 37 degree C day at sea level.

 

AMC VLA 613 ©

 

Material Strength Properties and Design Values (Acceptable Means of Compliance)

 

Test Temperature –

 

a. For white painted surface and vertical sunlight: 54°C. If the test cannot be performed at this

 

temperature an additional factor of 1·25 should be used.

 

b. For other coloured surfaces the curve below may be used to determine the test temperature.

 

Curve based on: NASA Conference Publication 2036

 

NASA Contractor Report 3290

 

 

What should happen is that when you turn 70 you should be freed from all the bullying nonsense which passes for "safety" regulation.Here's why...

(1) A 70 year old has a proven track record of survival. No 40 or 50 year-olds have proven they have what it takes to get to be 70. So the experts are the 70 plus guys and they should call the shots.

 

(2) Most 70 year-olds have finished work and therefore their passing will not be of detriment to the country. Not that they would be easy to get rid of if you refer back to point (1).

 

(3) It is about 5 times more risky, on mortality statistics, to be inactive than it is to fly. So anybody who who grounds a 70 year-old and makes him inactive is at best showing a lamentable lack of situational awareness and at worst showing a callous disregard for the persons life.

 

Regards from a young 69 year-old.

More truth in that than you may think; flying gives you an incentive to look after your health. I started flying 51 years ago; still learning. When you stop learning, it's time to quit.

 

 

Civil Aviation Order 20.18

 

Appendix I

 

Instruments required for flight under Visual Flight Rules

 

(Limited to aircraft specified in subsection 3 paragraph 3.1)

 

1 The flight and navigational instruments required for flights under the Visual Flight

 

Rules are:

 

(a) an airspeed indicating system; and

 

(b) an altimeter, with a readily adjustable pressure datum setting scale graduated in

 

millibars; and

 

© (i) a direct reading magnetic compass; or

 

(ii) a remote indicating compass and a standby direct reading magnetic

 

compass; and

 

(d) an accurate timepiece indicating the time in hours, minutes and seconds. This

 

may be carried on the person of the pilot or navigator.

 

2 In addition to the instruments required under paragraph 1, aircraft, other than

 

helicopters, engaged in charter or aerial work operations and operating under the

 

Visual Flight Rules, shall be equipped with:

 

(a) a turn and slip indicator (agricultural aeroplanes may be equipped with a slip

 

indicator only); and

 

(b) an outside air temperature indicator when operating from an aerodrome at which

 

ambient air temperature is not available from ground-based instruments.

 

Appendix IV

 

Instruments required for aeroplanes engaged in:

 

(i) aerial work and private operations under the Instrument Flight Rules

 

(including night V.M.C.); and

 

(ii) charter operations under night V.M.C; and

 

(iii) Instrument Flight Rules freight only charter operations in aeroplanes

 

with maximum take-off weight not greater than 5 700 kg.

 

1 The flight and navigational instruments required are:

 

(a) an airspeed indicating system; and

 

(b) a sensitive pressure altimeter; and

 

© (i) direct reading magnetic compass; or

 

(ii) a remote indicating compass and a standby direct reading magnetic

 

compass; and

 

(d) an accurate timepiece indicating the time in hours, minutes and seconds, except

 

that this may be omitted if it is carried on the person of the pilot or navigator; and

 

(e) a rate of climb and descent indicator (vertical speed indicator) for other than night

 

V.M.C. flights; and

 

(f) an outside air temperature indicator; and

 

(g) an attitude indicator (artificial horizon); and

 

(h) a heading indicator (directional gyroscope); and

 

(i) a turn and slip indicator except that only a slip indicator is required when a

 

second attitude indicator usable through flight attitudes of 360 degrees of pitch

 

and roll is installed; and

 

(j) means of indicating whether the power supply to the gyroscopic instruments is

 

working satisfactorily; and

 

(k) except for aeroplanes engaged in night V.M.C. flights, means of preventing

 

malfunctioning due to either condensation or icing of at least 1 airspeed

 

indicating system.

 

2 The instruments specified in subparagraphs 1 (a), (b), (e) and (k) of this Appendix

 

shall be capable of being connected to either a normal or an alternate static source but

 

not both sources simultaneously. Alternatively, they may be connected to a balanced

 

pair of flush static ports.

 

3 Except for aeroplanes engaged in night V.M.C. private and aerial work operations the

 

instruments specified in subparagraphs 1 (g), (h) and (i) of this Appendix shall have

 

duplicated sources of power supply unless the turn and slip indicator or the second

 

attitude indicator specified in subparagraph 1 (i) has a source of power independent of

 

the power operating other gyroscopic instruments.

 

4 A gyro-magnetic type of remote indicating compass installed to meet the requirements

 

of subparagraph 1 © (ii) of this Appendix may be considered also to meet the

 

requirement for a heading indicator specified in subparagraph 1 (h) of this Appendix,

 

provided that such installation complies with the power supply requirements of

 

paragraph 3 of this Appendix.

 

 

Which one would I be more likely to use in an ultralight?

I don't think the non-sensitive ones are acceptable. See CAO 20.18

 

 

Sensitive usually has 2/3 pointers with the longest indicating 1000ft per revolution.Non-sensitive usually has only 1 pointer and may indicate as much as 10000ft per revolution.

 

Then there are the ones that have 2 pointers and the long one indicates 3000ft per revolution. Found mostly in Eastern European gliders.

 

Robert

Yep. The 3000 ft / revolution ones are an adaption of 1000 metre/revolution.

 

All the Jet ones have them, as they don't vibrate much. You check them by putting the microphone (on intercom) on them and clicking the button. You can hear the rattling noise in your headset. A piston engine single wouldn't need that sophistication, for the reason you state. Nev

Ta - I don't get to play with that kind of hardware. In a glider, one normally taps the altimeter with a finger to see which way the needle moves, if you're in marginal lift. But I don't think that the incorporation of a vibrator defines a "sensitive" altimeter; if it reads 1000 feet per turn, it's a "sensitive" altimeter.