Category: Uncategorized

VNE – to dive or not to dive – that is the question

I conducted the air test recently. A cockpit full of cut down LAA air test forms (14 pages therein) .. all reduced in side to A5 and clipped onto the clipboard so that the open cockpit flight didn’t spray it over the Norfolk countryside like confetti !

This gave me all the 100s of checkpoints for the flight test that I could capture for the subsequent manual form completion on the ground (quite why we havent got an editable version of this or an online Database escapes me)

Strapped in and headed off for a tight climb up to 3,000′ and then power back and into the dive ..

I remember the first one of these i did in a Stampe SV4C over La Rocque on the SE corner of Jersey, my inspector Bob Wright sitting in the front with a big checklist .. shouting what he wanted next.

I started at 3,500 over the sea and actually ran out of height before we got to VNE as i chickened out of the hard push required and we had to do it all again .. Bob laughing away up front !

This one over the flat Norfolk countryside i pushed over and altimeter started to unwind.. the noise builds and wind rushes ever faster as you tuck yourself behind the windscreen and keep a good eye on engine revs to prevent overspeeding.

I started to ease out at 87mph and felt that was fine.

Im never going to go that fast between now and the next flight test in 12 months time.

Dutifully submitted all the numbers to the LAA only to have pushback on the VNE. Why handnt I done it and yes, I needed to reach manufacturer’s VNE of 100.

Today, on a pretty cold October day, ive just nipped up to 3,000 .. pushed harder and reached my paint marked 100 on the ASI

Updated details sent in, hopefully for the reissue of the FULL permit (currently flying on a temporary one to allow test flying)

As you may surmise .. im not a great fan of the VNE test

  • Yes the manufacturer has set this limit to demonstrate a ‘top end’ limit
  • Do I EVER fly anywhere near that limit in all my general day to day flying
  • NO
  • Maybe just over 50% of that speed is normal and achievable cruise speed with the current approved engines.
  • So why do we expect pilots to push the airframe to that once per year ?
  • Is artificially stressing the aircraft once per year deemed a good thing ?
  • Its not like a benign stall test that you can do at height and have loads of margin for recovery
  • At the bottom of the dive you have the potential for significant things to happen
  • Your margin and recovery options are, by virtue of that round out speed, limited
  • Recovering needs to be gentle and controlled and I would argue that recovery is another significantly critical phase of this manoeuvre
  • If a pilot does this only ONCE every 12 months surely we are failing the ‘recency’ measure the LAA put so much faith in ?

Anyway, rant over, one whinge isn’t going to change the world.

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Battery uplift

So, as the colder days begin.. the battery had decided to play up and starting has become a slight ‘fingers crossed’ affair !

Way back when I put the first battery in i selected a motorcycle unit that fitted neatly into the TLAC kit supplied tray.

This was mounted in front of the passenger seat but, on getting around to weight and balance, I realised I needed a lump of lead in the tail to get CofG in right place.

Having made a small mount for the lead and fixed it.. the LAA decided they didn’t like a lump of lead in the tail that could head forwards in a nose in crash so rejected my plan.

I then realised that the lead weighed the same as the battery I had, so had the brainwave of removing this pointless excess weight and putting the battery in the tail with a proper supplied battery mount. So, nice and secure but hey presto I didn’t need any additional weight to achieve equilibrium.

This meant I needed to run quite long power cables up to the starter solenoid and also an earth to the engine… and this, over time, proved problematic as the power loss over some 4-5m of cable was evidential

I started to look at the lead into the fin post idea but then hit on the idea of using the priginal front battery location AS WELL and connecting the batteries together… in series..

This gave superb starting and you just had to breathe on the push button starter and boom into life !

Roll forward through the years ..and motorcycle batteries aren’t great. They definitely have a shelf life after which you simply need to cycle them.

I checked back on the one that i had in the front yesterday and it’s 5 years old !

The £100 ish to replace far outweighs the disappointment of a none start !

The tail one i believe was done after I got to the UK and, the last time I did it, I made a small cut out Oratex panel that will allow easier replacement (the whole side of the aircraft being one complete piece of Oratex).

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Flight Test

So, after a few ‘fettling’ sessions as they are known.. where you fine tune this and tweak that ..you reach a point and a day.. where aircraft, engine, weather and time all co align and you can carry out the flight test.

The Light Aviation Association (LAA), the governing body for homebuilt and other registered aircraft, have a plethora of forms and process that you need to follow on a regular basis to ensure your annual update is up to spec

Add into this the fact that yiu have had ‘an upset’ and this brings in additional checks and balances

All very sensible stuff to ensure you have ticked every box and thought of as many eventualities you can.

The ‘changes’ to my aircraft, post the incident, meant that I needed a full flight test. 14 pages of check items to run through.

I cut all these 14 pages into manageable half pages so that I could have them on my knee board in the cockpit and then attempt to capture all key information during the test flight.

The problem with lots of bits of paper in a small open cockpit is that its a bit blowy and tricky to keep your notes !

The initial power out climb was a very long slow orbit slowly climbing at a constant attitude for nearly 5 minutes.

The old overheating of the cylinders was pretty much gone and I timed each 500′ ad it went.. turning out to be about 600feet per minute

Once I reached 3,000′ it was getting quite chilly and so all temps were looking absolutely fine. I then captured all the vakue on the way up and then eased the throttle back and into a dive

The aim of the dive is to check VNE .. ie never exceed speed .. which is 100mph.

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Torque check

Having had a the dreaded flu for a few weeks it was time to check the torque settings to update the log book during these early test flights and getting her ready for the air test.

With torque set to 32nm pretty much every bolt was spot on .. one or two took one extra crank to bring them up to spec.

Jabiru are renowned for wandering out of torque and it only takes about 20 mins to check all the bolts .. remembering the hidden one inside the rocker cover behind the small grub screw.

One thing I’m not mad about is the lipstick

Its calibrated for the Jabiru 2200 BUT in trike mode … and the Ranger obviously sits on the tail. This means you are constantly making that mental switch on reading.

The sunp is so pitifully small anyway and James (the Chief engineer at TLAC) always used to say just put a piece of thin wood down to the very bottom to see what is actually in there !

Keeping a very close eye on oil levels as I run-through the first high powered climbs and check it on cool down EVERY flight

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Overall flying locations

Over the years its been great to have the chance to fly lots of places with many many people …

Even though the advent of airborne GPS was a relatively late addition for me, apps like SkyDemon have been a revelation

They have simplified not only advance planning but in flight changes due to usual bad weather that usually ‘unexpectedly’ happens in the UK

I was delighted when Skydemon further developed their already amazing software to add auto route tracking over time with a map overlay

This shows mostly Jersey based starting points and flying to various places in amd around the UK as well as France and Luxembourg .. many small airfields with friends to pickup pups or business trips to various European offices

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Flying videos

Its so nice flying out of such a friendly local airfield .. always someone around to lend a hand, pass on great skills and be that friendly guy who takes the trouble to video some of your initial circuits post the rebuild

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Hands up …

One of the tests after (significant) changes to an aircraft is a full flight test … before that..you just want to know “Does it still fly straight and level” .. without too much heaving on the stick.

A small test i did on Monday was to get up to around 2,000’… wind on the ground was varying between 11 and 18kts so it would be a bit stronger up there…. and LET GO !

Looking at little like a hijack (but no gun involved 😉) i trimmed, let go of the stick and did a 1 min 14 second turn….hands off .. just judicial use of a bit of rudder to coax her around

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Cooling – Next Check

Id been thinking about the hot running head and thought the damage to the lower cowl meant we needed to repair and beef up some of the lower curves.

The original holes in the lower cowl were primarily around exhaust exits, a small hole where the exhaust silencer block touched the cowl, the oil radiator and feed pipes and some cut outs to accommodate the cylinder heads.

The accident crunched the oil radiator into the lower curves of the cowl and that needed beefing up and neatening

The net result was a super strong and great gloss finish but some holes were either enlarged or simply aren’t required anymore.

To test my theory out, without the need to do any ‘hard acts’ on the cowl , I planned to use tape to temporarily block off some of these holes and double the tape so that it would survive a short (30 min) test flight.

A short test flight, which ended up being 41 mins, proved very successful.

Even powered climbs were better than they were before.

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Test flying – Part II

Having left it for a few hours and thought about things .. one thing that came to mind on the cooking was the only major thing I changed on the engine following the ‘downing’

That was a brand new oil cooler matrix ..the original being the only part of the aircraft to take the brunt of the field landing !

This left the old matrix somewhat mashed …i removed it as it was leaking oil in the field on recovery.

What I didn’t do .. was take a photo’ before I removed the old unit and the pipes fitting could easily have interchanged

So, Plan A, is to switch the pipes out of the TOCA, the theory being .. if I had the pipes the wrong way the oil would have to be pushed ‘UP’ from the bottom of the oil matrix vs a gravity style ‘in the top’ method of circulation.

Pipes have been switched, so awaiting good wind direction and strength for a retest

Part II – investigation continues …

So, I thought if the TOCA was causing some sort of problem, ie the thermostat was perhaps causing an issue, I would remove it .. like you do with a car .. and the oul just flows .. uninhibited … right?

Anyway, removed it, its under a little square plate and easy to remove. Test flight number 4 (without the thermostat in place) and 3 minutes into the flight the oil temp started to climb past 80

Pulling around, throttling right back and brought her in on tickover.

On checking with the Jabiru guru Kevin H… it turns out if you remove the thermostat it CLOSES the feed .. completely!

So although this wasn’t what was required it PROVED what was wrong !

I suspect the thermostat valve is STUCK and needs freeing … then putting it back in for another check

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Test flight – post the rebuild

The day finally.arrived, where the paperwork just about exceeded the weight of the aircraft and, all being duly signed, Tom my inspector handed me the clearance paper.

This had already been pre signed by the Head chap at the LAA – major repairs and new builds seem to go through a slightly escalated route to the normal annual update.

The wind on Saturday would have been fine a while back .. 8 or 9 across ..but I didn’t want wind to be a factor at all post the 12 month + rebuild and today, Sunday, it as around 4 across.

Having checked the walk-around for the umpteenth time I had pre fuelled on Saturday, with 20L in the top (holds 36) and 20L in the main (holds 40), i finally pulled her out for start up.

I started up and warmed up and took off with no problems… scooting down the runway to climb out to the North and into the 500′ circuit. The aim was to keep the first few circuits close and ‘glideable’ in case anything was to happen.

A few minutes airborne and a couple of touch and goes, and it was time to come back into the circuit and land. It’s so easy to land this aircraft 😉 so ended up doing a couple.

Leaving it to cool, I removed the top cowling to check all was well in the engine department.

On the 2nd flight I noticed that the oil temp was rising a little on full power as was CHT no 4 …. this was only when pushing the engine a bit (3,200 rpm vs cruise or 2,700) so landed to check.

There was nothing obvious but, I wondered if perhaps the TOCA, the block that prevents cold oil being pushed around the engine (until its up to temp – of 50c, after which the valve opens and lets oil flow through the matrix), had a stuck valve ?

I decided to remind myself of what the TOCA did in terms of functioning, so checked my own blog !

It was simple to remove the thermostat and refit the blanking plate. I can run without this in the summer as the engine quickly gets up to running temp anyway.

The 3rd flight – video below, was a test without the thermostat, and climbed out with a bit more confidence and climbed up to 1,000′ in a slow circling left hand turn.

Passing through about 700 the oil temp started to rise to the high 80s (max is 90 to 100) and the CHT 4 started getting up to 180 vs the 160s of the other 3 Cylinder heads.

I landed back with tickover down to a close right hand base.. keeping the engine cool.. all the way down.

This time on landing i killed the mags quickly on parking and undid straps and jumped out to check the oil feed pipes into the cooler matrix .. both pretty cold !

I parked up and let the whole lot cool down whilst I thought what it might be.

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