General aviation is widely accepted to be in somewhat of a decline in South Africa. Thus it is quite exciting when an exhibition aimed primarily at the general aviation sector is scheduled – look, it’s not Oshkosh or Sun ‘n Fun but this is about as good as it gets for us locals. It is also quite unusual in that there was no airshow scheduled – only static and trade exhibits. The exhibition is Aero South Africa and it was billed as an offshoot of Aero Friedrichshafen
The other day I offered to help one of our club members to move his aircraft to another airport for its MPI/Annual. No problem, right? Except it’s a controlled airport I’ve never landed at before (at least during the day – I did a touch and go there on my night cross country but the tower was closed).
This did give me some room for pause – it’s an easy airport, 2 runways, wide runways but there are some issues. Firstly, the airspace is busy – there are a lot of flying schools on the field and a fair number of commercial GA operations. Secondly, the airport is crammed tightly against the Class B (TMA) airspace of O. R. Tambo international airport (FAOR) and they don’t take kindly to bugsmasher’s violating their territory.
It is a year since I passed my initial flight test for my PPL. According to South African air law, after one year, you need to revalidate your PPL (and thereafter every two years). This is done via a ground briefing/exam and a flight test.
In the year since I got my PPL I have flown about 70 hours, 11 of that as dual instruction for my night rating and 5 odd hours in the sim. The rest, apart from a few jaunts in the SR20 with family, has been in my Sling 4 ZU-IBM. There have been a lot of local flights – practicing stuff, keeping current and proficient, and the odd long trip – most memorable being the flight to Cape Town and back in November last year, with a few family day trips thrown in here and there.
My airplane needed to go to the AMO to have some work done. This, as most aircraft owners will appreciate, is a real pain. To achieve this 10nm flight requires two adults, at least one car and a fair bit of patience from the non flying adult.
The usual rigmarole – drive to Baragwanath airfield. Drop off flying adult at Baragwanath. Non flying adult drives (usually in rush hour traffic) to Tedderfield while flying adult preflights and flies the aircraft to Tedderfield. Both adults then drive home. Understandably, this plan is not too popular with the non flying partner because it can be a 2.5h exercise when we have better things to do.
May and June are busy months from a flying admin point of view. My medical (which needs to be done annually) expires at the end of May. My PPL needs to be renewed by the end of June. This makes this a busy couple of weeks.
To renew my medical requires an annual audiogram, lipogram and eye test. To be honest, I can’t see why these need to be done yearly (perhaps with the exception of the eye test?). Having to go through a medical every year at my age (42) seems superfluous – especially since I know I’m in good health.
It’s a public holiday – Worker’s Day and those of us who work are restless to get some air between us and the ground. There is some discussion in the club WhatsApp group about a suitable location for breakfast – some guys want to go to Thabazimbi for the NGK Meifees (May fest) but many of us are a little twitchy about flying to a town airfield and leaving our aircraft there, being transported to the festival ground and having to rely on folk to bring us back to the planes again.
Oil. It’s quite important stuff in engines, especially in aeroplane engines. Considering the only thing keeping us up in the air is the engine it makes sense to keep a close eye on the oil.
He who is without oil, shall throw the first rod
I have an issue with a low oil pressure reading. It would be less irritating if there was some oil floating around in the cowling, or a stripe down the fuselage, but no. Not a drop.
Initially it seemed like the pressure dropped with altitude which made us suspect that there may be an issue with the breather pipe, but the oil system on the Rotax is somewhat more complex than the wet sump on most aviation pistons. The engine is a dry sump system. The oil resides in the oil tank (perhaps unsurprisingly) and is pumped from there to the oil filter via the oil cooler by the oil pump which is driven by the camshaft. Oil returning to the sump is pumped back to the oil tank by blow by gases, the Turbocharger has oil pumped via a secondary line and the oil drains from the turbo sump to the oil tank.
The oil pressure is measured by a sensor ‘distal’ to the pump and there is a pressure regulator. The pressure regulator may be the source of the issue – it contains a spring and a ball bearing which regulates the pressure. When we looked at the engine analysis graphs again it appears that there is a better correlation between oil pressure and oil temperature, rather than altitude.
This may mean the problem is easier to solve. Maybe. As temperature increases the viscosity of oil decreases – which may make it harder to pressurize if there is some issue with the seal, pump, oil cooler bypass etc etc.
What this really needs is someone with real know-how to test fly the aircraft, possibly also inserting a mechanical Bourdon tube type gauge into the system and comparing pressure readings. What I wanted to do was to try and replicate the problem with the altitude factor removed – and this would mean flying in the pattern at high power until the oil temperature rose enough to decrease the oil pressure.
So this is what I planned to do. Of course, having an issue to solve on the aircraft almost certainly means that no time will be available to fly so it is 10 days later and time to test fly. That was the plan anyway. Of course, on arrival at the airfield I found it blanketed in mist despite the late hour (9:30am). Not a problem, I had another job to do and that was to try and get a fuel stick calibrated.
I had a great idea for this job – take a hose pipe, stick it into the tanks, siphon out as much as I could then sump the rest out. Well, that plan did not work at all. Firstly I could only siphon 25 litres from the tanks before the hose was uncovered and I couldn’t push it further into the tank (admittedly, I was loathe to force it in in case it did damage to the float gauge). Also, siphoning petrol is no fun at all. I got quite a lot of fuel in my mouth and in my nose which caused me to smell like I was living in a fuel tank for the rest of the day.
I decided to compromise and drain until the area directly below the filler port was dry ( ‘to tabs’ if you will) and then measure how much fuel it would take to fill the tanks to the brim again. With a known tank capacity (84 litres) I could subtract this amount and have the fuel level at tabs. As it turns out, if the tabs are dry, there is less than 35litres in the tank. Good to know. I like having some kind of scientific estimation of fuel tank volume. I used a big piece of wood, marked it as I filled the tank 12.5 litres at a time and then transferred these marks onto a wooden dowel stick.
While I was sorting this out, the fog had lifted to low overcast but that seemed compatible with circuit flying so I started up and headed out. On climbing out from the field I couldn’t help but notice the rather large storm approaching about 30km away – this was going to put a spanner in the works. Still, I was able to do about 5 circuits at high throttle settings, getting the oil temp up to 82 Celsius / 180 Fahrenheit- without causing a low oil pressure alarm – the pressure did decrease though – as shown in the Savvy graph below.
The incoming storm put paid to the 30min flight I was hoping for and I put her down very quickly – into the teeth of the Cb outflow – not my best ADM moment but safely down and we crammed the plane into the hangar just as the first drops were starting to fall.
There will be no flying for the next two weeks but after that I’m popping IBM across to the AMO for the oil change and they will check and possibly change the oil pressure regulator – which will hopefully sort out the issues. To be honest I think it needs a climb to altitude and thereafter a throttle back to allow oil Temp to decrease a bit to fully troubleshoot. Time will tell. In the meantime, I need to wash my hands. Again. Blood petrol….
Yesterday I was fortunate enough to be able to take my friend Ari flying. He may not know it but he’s actually my aviation mentor – one heck of a nice guy who has a knack of thinking about general aviation in ways I haven’t thought of. He’s a commercial instrument rated pilot with more than 1500h and he flies a FIKI Cirrus SR22T with his father.
One reason we are buddies is that we have similar outlooks on general aviation safety and doing GA correctly. My feelings on these are borne out of lots of reading – his I suspect are from lessons learned in years of flying. It can be daunting flying with a significantly more experienced pilot in a non instructor/examiner situation (OK, it can be very daunting flying with an examiner) because one feels like one’s skills are on show – this was the first time I was to be PIC in my aircraft with him (I’ve flown in his aircraft many times). You don’t want your first flight with a new passenger to be your last flight with that passenger..
I must confess to feeling that the Sling was a little shabby compared to the extremely well equipped G5 Cirrus but hey, an airplane is still an airplane – and I’m a proud owner.
We had a secondary objective and that was to test the Aerox system I acquired recently – it seemed prudent to do this with an experienced supplemental oxygen user. We came prepared – he had 2 oximeters and I had 1. Of course, true to form mine was DOA, although after 10years of hard use in my day job meant I shouldn’t be surprised. It is time for a new one anyway as the LCD display isn’t very readable in the bright cockpit. In addition we had an emergency cylinder in case the main cylinder didn’t perform as expected.
For a change the weather was playing along really nicely and although the visibility wasn’t really good, the air was smooth as we climbed energetically away from BaraG – had a good 750-800fpm climb rate which impressed my passenger. There was no other traffic in the training area and we started our climb after exiting from under the Johannesburg TMA. Information approved our climb and handed us over to the area controller (Centre) and I handed control over to Ari. For the last day in March it was still pretty warm – was showing an OAT of 21 Celsius at 10000ft but the Sling trundled on at 400fpm through 11000ft with the Airmaster Prop in Climb and 34” manifold pressure on the throttle.
We routed south as we climbed, out over the Vaal River and Parys, enjoying the views (despite the limited vis) and the smooth air. Climbing through 10000 feet I popped the pulse oximeter on and was quite alarmed to find my sats were 89%. I wasn’t expecting it to have dropped so low at a relatively low altitude. I didn’t feel any adverse effects although I don’t believe time of useful consciousness is an issue at this altitude. However, it seemed like a good idea to get the oxygen on which we did.
Let it be said that one looks a little ridiculous wearing an oxysaver cannula – but you look a lot less ridiculous with the cannula on than slumped over the controls with two fighter jets on your wing. The oxysaver allows pretty low flows – <1litre per minute at altitude up to 15000ft – by using a small reservoir so it’s relatively economical to run once you’ve forgotten the initial outlay for the equipment!
Area control came on asking us to stop our climb at FL125 due to other traffic on the airway above us which was a little disappointing but the density altitude was already well over 14000ft by this time, so I didn’t think with a service ceiling of 16000ft we’d get much higher anyway.
At this point we noticed that the oil pressure had decreased to 1.6bar from 2.5bar. Lower limit of normal is 2bar on the Rotax 914UL. This was obviously not something to take lightly. Initially we thought it could have been due to the warm conditions – oil temp was normal and CHT’s were within limits. Still, we arrested the climb and throttled back with no improvement. The best call at this point was a 180deg turn and route back to home base keeping a good lookout for potential off airport landing sites.
We had to descend to avoid busting airspace and as we descended below 9500ft the oil pressure recovered to normal and stayed there, going up to 3bar as we leveled off at 7000ft. Given that there was no other indication of abnormality we felt it was reasonable to do some maneuvering while keeping an eagle eye on the engine gauges.
I did two steep turns (PPL standard @ 45deg) and thereafter Ari did 2 at CPL standard (60deg). That man can fly an airplane – made the wake on the second attempt in an unfamiliar aircraft. He was raving about the control responsiveness and the inherent balance of the Sling – I think he was quite impressed – high praise indeed from someone who has hundreds of Cirrus hours. “It feels like I have an RV Grin,” he said as we cruised back for the overhead at Baragwanath. I dubbed it the “Sling Smile”
One touch and go then a full stop landing and it was time to put the plane away. I did get some constructive criticism of my crosswind landing – I need to try and land upwind of the centreline rather than ON the centreline – this makes sense as it gives one a few more metres to deal with any squirrelly behaviour after touchdown.
All in all a successful morning’s flying. The oil pressure reading remains a concern but I’m waiting on the AMO to comment. We suspect it may be a grounding issue or a problem with the oil breather pipe. We had a good look around the inside of the cowling and there is absolutely no oil leaking anywhere and no oil stain on the belly of the plane. Time will tell – the joys of aircraft ownership…
I was supposed to fly to Middelburg(FAMB) this afternoon to camp at the AeroClub of SA Airweek being held there this weekend. The weather, it seems, had other ideas.
I was delayed by 30min at work this morning and by the time I arrived at the airfield the storm line was developing. I hung around finding things to do on the plane until 16h00 local by which stage I could probably have found a route but the flying time would have meant an after dark arrival – and I’m not night current at the moment – not landing at an unfamiliar field at night thank you very much.