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2020 - 51.1 hours & 87 landings

2021 - 38.6 hours & 52 landings

 

Virtually all flights were within 80 NM of South Grafton. Casino, Lismore, Evans Head, Coffs, Tabulam etc except one flight to Boonah. Yep the local area is very familiar these days.

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I retired three years ago and since then I can’t find the time to fly,  I wonder how I ever found the time to work 

100 hours again this year, my average over the last 17 years is just over 104 a year, best year was 147 back in 2018, not bad for someone who doesn’t have weekday access due to the RAAF activation and

What you must consider is fatigue and deterioration in older aircraft. Look at the Blanik. they all ran out of frame life. Pressurised hulls can only take so many cycles and then they are grounded. A

You are more the average, kgwilson.

I reckon that Nev is right again and hours ain't hours, well not all hours are the same. My new Jab has an autopilot and when that is doing the flying, how can you compare that hour with say an hour doing circuits  or aerobatics?

AND, to confuse things even more, there is the possibility that not all hours are properly logged on account of how logging hours brings up maintenance costs.

I know that nobody here would even think of doing such a thing, but I also know a service guy who says that private hours in the log need to be doubled to get the reality.

Apparently stock roundup helicopters in the top end have come to grief by overdoing this tactic.

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When materials and machines are made to standard, it’s in the nature of some people to push the limits, in the belief that there is a large “fudge factor” to protect you. 

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“Parker Pen” hours used to be common! 

The ‘true’ measure of hours should show up on a flight test, they are just numbers at the end of the day.


I could add up all my hours in my several log books and come up with a different answer every time probably! Mistakes get made over many years of adding. Once upon a time I used to love doing log book entries, we paid enough for them, now it’s a chore!🙁

To stay reasonably on top of the game means keeping yr head in the books year round & driving a plane regularly👍

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Sadly, 2020 and 2021 weren't great years for me.. While I managed to keep flying in 2020 (just shy of 100 hrs), 2021 was a rather bare cupboard. Apparently, while I classify flying as a staple, the Financial Director (aka wife) considers it at the top of the discretionary spend that can be cut. Well, you know the ol' saying.. happy wife, happy life. But, onwards and upwards, and I am negotiating a purchase of another shareoplane (TB20, again), and with the mild wx we have had in blighty; with a new medical I can only see another 100+hrs this year.

 

Re hours aren't hours, well, it depends. I try and make each flight a learning experience... I have flown autopilot many times and used the time to brush up on visual and dead reckoning navigation. Even as a passenger of a light aircraft flight (or just operating the radio), I am going through the flight in my head, learning fro the other guy (sometimes, what to do, and sometimes what not to do).

 

As long as one takes the approach that they can learn something from every flight, and they critically assess what happened (even on uneventful flights), well, each hour can be productive.


Hope your 2022 flying is safe and enjoyable, regardless of the hours you fly.

 

Edited by Jerry_Atrick
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Old K, your point is a good one and more true for wood and fiberglass planes than metal ones I think. Once I saw the Janus fatigue-test rig at RMIT in Melbourne.

It was being abused far more than any real-life plane I had ever seen, and the reason was that they had measured the wing and found it was 5mm thicker than designed.

Any natural or hand-made thing has a range of strengths, so of course the authorities have to apply a big fudge-factor.

Here's another example.... "smooth air" can, I have been told, contain a sharp-edged upgust of 15 knots! In all my 3000 hours of gliding, I only found a thermal that good a couple of times.  And that was flying on good days and looking hard for thermals. This makes me wonder about all the ASI markings we live with. And, it makes me wonder about if that fudge-factor has been made too big.

 

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What you must consider is fatigue and deterioration in older aircraft. Look at the Blanik. they all ran out of frame life. Pressurised hulls can only take so many cycles and then they are grounded. A weaker point will take most of the fatigue in a cantilever structure. Another structural problem is Hangar rash. If you are already pulling "G" and hit a gust it's multiplied. I've flown F-27's that had extensive fatigue cracks. THEY just keep a close eye on them . I'd rather they didn't exist.. Planes near salt water corrode like you wouldn't believe.. Nev

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Steel has a stress level below which fatigue does not exist.  Aluminium does not have any point at which does not fatigue.  The design level is statistically derived with a nice safety margin....however is your aircraft aluminium as per design?  Inspections are important.  As Nev commented salt erodes aluminium and I think that it reduces the fatigue failure points (not sure).

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Thinking about the fatigue in aircraft brings another question to mind.  The designer of the Cozy IV stated that composite fibreglass does not fatigue.  I don't know that I believe him.  Anybody know anything about composite aircraft fatiguing?

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1 hour ago, Geoff_H said:

Thinking about the fatigue in aircraft brings another question to mind.  The designer of the Cozy IV stated that composite fibreglass does not fatigue.  I don't know that I believe him.  Anybody know anything about composite aircraft fatiguing?

Originally (at the start of the plastics industry) boats, chairs, truck bodies were made out of "fibreglass". Some people were confused as different variants were used, so it became "Fibreglass Reinforced Plastic" (FRP) so a little similar to concrete, a thermosetting plastic reinforced by glass strands (glass balls melted and pulled/teased out a long distance to make thin strands. (I think the UK called it Glass Reinforced Plastic (GRP).

 

Next there were variables in both the reinforcement and the plastic.

 

The reinforcement could have the strands chopped into about 30 mm lengths then blown over a table until the layer reached a certain height expressed in weight, so 3 ozs Chopped strand matt or 6 ozs chopped strand mat. The matt was held together by a temporary glue.

 

If you wanted additional strength in a particular direction you could use rovings where the molten glass was extruded through a die and twisted like a neat rope finishing up around 3 mm diameter. If you wanted to make a collar with a flange you could lay uo chopped strand mat for the tube and flat sections, then wind two or three turns of rovings around the 90 degree join.

 

If you wanted something stronger in tension you could use woven rovings; rovings woven to make a sheet.

 

You could also reinforce the resin with ms flat, angle, aluminium extrusion etc., kevlar and carbon fibre.

 

There is also a big range of resins starting with all purpose laminating resin, easy for the hobbyist, and ranging to fast setting resins, slow setting resins, resins filled with steel powder, non slip properties and so on.

 

The whole family has become known as composites.

 

So when you ask about composite aircraft fatiguing you have to consiider what the resin is and what the reinforcement.

 

Weight for weight FRP is stronger than both steel or aluminium. Boats built to a price with a thin laminate and crap resin can start cracking after about three years. Truck bodies built with a heavy laminate using high grade polyester resin are still running around after 60 years road use.

 

A 3 ozs layup of flat sheet using chopped strand mat, bent up and down to a certain degree will have a memory - come back to its original position (with a high quality resin) for years without weakening or failing - the strands of glass are held by the resin and at that stage they are just bending because they are flexible and stretching. If you bend the sheet beyond that stage the glass strands on the outside begin to snap. All the others still have memory and you can go on bending it at that stage; you just have a slightly weaker structure. As you go on more and more fibres snap in tension until you reach a point where at the highest stress point all fibres have snapped and a piece falls out or an end falls off.......but the part where fibres haven't snapped springs back into place.

 

This process is repeatable, so you can test for failure point and engineer a structure that will live up to that point, iven the same materials and the same quality of labour laying up the laminate.

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Thanks, great information.  I am only aware of people making composite aircraft using a skin of epoxy glass or foam with a fibreglass double skin.  With the exception of the very advanced aircraft construction similar to the Boeing aircraft.  I have been building using a foam covered with glass/epoxy.  I have been unable to determine the strength of the combination by calculation.  I quess a combination, construct it and then test to destruction and use the values found in the test as the value for design.  I think that finite element analysis maybe the way to go.  All my tests have failed by shear stress at the centre of the foam.  The layers of glass/epoxy remained intact in the testing, but it was deformed.  

But will the structure take significant cycling? Will it fatigue?  Maybe I should make a test rig.

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2 hours ago, Geoff_H said:

Thanks, great information.  I am only aware of people making composite aircraft using a skin of epoxy glass or foam with a fibreglass double skin.  With the exception of the very advanced aircraft construction similar to the Boeing aircraft.  I have been building using a foam covered with glass/epoxy.  I have been unable to determine the strength of the combination by calculation.  I quess a combination, construct it and then test to destruction and use the values found in the test as the value for design.  I think that finite element analysis maybe the way to go.  All my tests have failed by shear stress at the centre of the foam.  The layers of glass/epoxy remained intact in the testing, but it was deformed.  

But will the structure take significant cycling? Will it fatigue?  Maybe I should make a test rig.

You're talking about a "honeycomb structure". If you produce a flat slab and try to bend the ends down, the top skin will be in tension and the bottom one in compression; the thicker the "honeycomb" foam the greater the strength, but bonding of the skins to the foam is critical to prevent the lower skin to buckle away from the foam.

The answers to your questions are "How long are the pieces of string?" because you haven't specified the type of foam - polyurethane gives a lot greater strength than polystyrene for example, and you are talking about epoxy vs polyester resin.   I would recommend you look for a book on composites and honeycomb structure; we had a leg each side of the razor's edge and did our own design testing becaise we were breaking new ground in a new industry, but by now I would hope there's a lot of design data. I would recommend you make your test rig, because although you can select all the materials and quality of materials from a recommended combination, there's a skill in laminating procedure which changes the final strength quite a bit - maybe as much as 30%. We used different laminators for different jobs; the best laminators who got the best resin penetration and reinforcement position on the most critical jobs.

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It is a polyurethane foam with glass/ epoxy skins.  Attachment to the glass epoxy using a glass balls/epoxy mix, that never failed.  The foam failed in shear at the centre.  I have searched for data on composite strengths, the best advice I got was that data was very expensive to get and guarded very much.  Some years ago I had organised to do a Master's in Aeronautical, my project would be to determine a calculation system for composites.  I got a contract just as I was about to start, never got back to it.   Too old now.

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7 minutes ago, turboplanner said:

…there's a skill in laminating procedure which changes the final strength quite a bit - maybe as much as 30%.

Working solo it’s easy to overlook minor blemishes. The quality of my current laminating job is better than some past ones; this time my wife has played a blinder with the roller.

 

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IF you sleep like a baby you'd need plastic under your sheet. Really thin sheet metal AL is difficult to get a long life. It doesn't rivet nicely and bonding as well would help spread the stress points. A scratch will initiate a crack.. The Jabiru are a proven safe structure and able to be rebuilt when extensively damaged. A tube steel triangulated frame is virtually everlasting if internal corrosion doesn't occur.. Nev

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3 minutes ago, facthunter said:

... The Jabiru are a proven safe structure and able to be rebuilt when extensively damaged…

Lots of crashed Jabs have been repaired and are back flying. Metal aircraft may cope better than composites with being parked outside, but a prag is often curtains for them.

I was shown a small section of a Savanna, the only bit that wasn’t bent by a simple prang.

 

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39 minutes ago, Old Koreelah said:

Lots of crashed Jabs have been repaired and are back flying. Metal aircraft may cope better than composites with being parked outside, but a prag is often curtains for them.

I was shown a small section of a Savanna, the only bit that wasn’t bent by a simple prang.

 

There have been plenty of myths in all of this. The fundamental truth is that weight for weight FRP is stronger than steel (so carbon and kevlar are stronger again.

The next step is how both are engineered, and a fully triangulated and plated space frame could well be much stronger than an equivanelt weight layout in FRP which just follows the outer shape but with a few braces.

On the other hand we would expect a fully engineered monococqe FRP layup to beat a space frame with missing triangulation and anti peel strips etc.

So the result depends on who designed it, what the materials sub specifications are and who built it.

 

The next factor is the severity of the crash.

The FRP has a memory right up to the fracture of the layup, and then there's no resistance - just a big hole where a frame/skin used to be. That can kill you.

A space frame will start to buckle and bend but is still resisting the crash all the way to the point where the crash stops. That can save you.

 

The next factor is how far the occupants move. If the harness mounting points fail the occupants may not survive a crash which the frame would have protected.

 

The Jab story may have come from a publication where a pilot had made a forced landing in an orchard and survived without injury. He had followed his training advice and aimed the aircraft between the trees, tearing off both wings. The fuselage didn't hit anything, there wasn't a scratch on it. The publicity story expounded what a strong aircraft it was becaise the pilot had hit trees and survived, and virtually no one picked up on the fact that the pilot had followed protocol instead of stalling it from height in a panic, nor did they point out that the real advantage was that the wings could be stripped and fitted back into the moulds to laminate the sections destroyed whereas aluminium wings would be a write off, and because of the material's memory every bot hole would match any replacement brackets.

 

On the other hand there was a photo circulating of a landing in SA across a cultivated paddock. The oscillation of the Jab had broken the A Pillars off at the top. The engine and cowl then fell into the dirt leaving the pilot and passenger out in the open, their knees forming the bumper for any solid objects if the momentum continued. That was a once in a million, but shows that you have to be careful about an overall grading of one form of strength vs another.

 

Regarding the bent Savannah frame, with a space frame you can strip the aircraft back, cut out the parts damaged, and replace the damaged frame section yourself, or order a jig built frame section and weld the section in (if you are not qualified structurally this may still require hiring someone to do the welding). With an FRP construction, you have to strip the aircraft and send the parts back to the factory to relaminate, so there's more labour. If the damage is covered by insurance the difference becomes the time and place of moving the aircraft.

 

 

 

 

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26 minutes ago, turboplanner said:

There have been plenty of myths in all of this. The fundamental truth is that weight for weight FRP is stronger than steel (so carbon and kevlar are stronger again.

The next step is how both are engineered, and a fully triangulated and plated space frame could well be much stronger than an equivanelt weight layout in FRP which just follows the outer shape but with a few braces.

On the other hand we would expect a fully engineered monococqe FRP layup to beat a space frame with missing triangulation and anti peel strips etc.

So the result depends on who designed it, what the materials sub specifications are and who built it.

I did heaps of calculations on which is lighter an epoxy/ cloth design or aluminium.  Strangely aluminium was the lightest, for a very unusual reason.  The shear stress of aluminium is around 60%of the UTS.  With any epoxy/cloth the maximum shear is the shear stress of the epoxy, after all that is in shear between the layers without cloth holding it together.  When I designed the main spars they were heavier than aluminium by a significant amount, just to ensure that the spar would not fail in shear.  A lighter spar could have been made using a carbon/Kevlar intertwined cloth.  Still a little heavier than aluminium.  The monocoque shell needed a foam core to get a good Euler's buckling force.  Boeing don't use epoxy, a much high strength "glue".  I am however a proponent of FRP.

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There was a Jabiru in SA which "landed" in a vineyard.

Apparently the student pilot turned off the fuel when doing his pre take-off checks. There was just enough fuel in the bowl  to get airborne and past the runway. I'm pretty sure they were uninjured because the instructor took over and they came down between rows.

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I’ve deliberately left the fuel tap off in one of my Jab donk powered machines to see how long it would run for. Doing a proper run up & warm up would see the engine quit well before being flight ready.

 

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I can recall a bloke in an ultralight at Beverley, W.A. (late 70's or early 80's), who took off with his fuel tap turned off.

He got to an altitude of about 60 or 80 feet before the donk stopped completely, and the resultant rapid return to terra firma was just enough to ensure a fatal result.

And the most ironic part of the whole story? - he was a former aircraft crash investigator with BASI!

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You need to "Prove" a new tank selection. An unfamiliar plane is time for a double check. It is surprising how many times the fuel is just enough to get the Plane airborne. IF the selector is left as you found it in the hangar, it would probably result in exhaustion before all the usual checks and run up and taxiing are done but if it's done just before take off, you are in strife. Most pre take off checklists have "FUEL"  as an item so you may fiddle close to the take off roll.. Nev

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Mine when training was "TMFIHCL" (Too Many Flying Instructors Have Crash Landings) T=Trim set for takeoff, M =Master switch on Both batt & alt, F = FUEL sufficient for flight, correct tank selected & selector to ON and Flaps set to takeoff, I = Instruments DI, AH, ALT set, Ts & Ps in the green, H= hatches & harnesses, doors all closed & locked everyone strapped in, C= Controls fully free, Carb heat cold, L=Lookout check everything clear for takeoff.. I've never forgotten it. Of course there are different things required in pre takeoff checklists for different aircraft.

 

Of course the Fuel part when in the Archer was Pump On, Select Tank, Check pressure, Pump Off.

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