STAYING ALOFT

Clive Davidson looks at how to manage a flight with only partial power…

Once established in the cruise, straight and level and en route, the task of piloting is probably at its simplest. It is also possibly the most enjoyable as the scenery slips by on track, features coming up on time, radio chatter routinely straightforward, and the ‘housekeeping’ checks presenting a picture of total normality. But... what if this blissful situation is shattered by the engine suddenly starting to run rough!

The old heart misses a beat or two for sure, but hopefully you quickly regain your composure, and keep flying the aeroplane. Is it slowing dramatically? If it is, then set it up in as gentle a descent as you can while you run through the checks – carb heat, mags, mixture, select an alternative fuel tank, all may provide Above All’s well with the world, it’s a great day, you’re in the cruise, running sweet and watching the world sail by... what could possibly go wrong! an answer as to the cause – and with luck a remedy.

The secondary checks of oil pressure and temperature, CHTs and EGTs, provided you have them available in the first place, really only add a suggestion of the cause, and little chance of setting things back on the road to the utter relief of normality.

These actions take but moments to complete and, if they achieve no sign of improvement, then decision making very quickly raises its head – the engine is running rough and you must decide what your next move is going to be. So: 1. Do you have an engine problem that you can solve? If yes, then having sorted it, either continue as planned or, if not wholly satisfied that the problem has definitely been completely resolved or you are feeling a bit jittery, divert to settle yourself down back on terra

firma and talk, consider, analyse and think it through logically. 2. If you can’t sort out the engine problem can you: ■ Still reach the intended destination. ■ Divert to a nearby airfield. ■ Or do you put it down in the best field you can see or find?

To a large extent, your answer will be based on whether or not you can still fly safely and maintain height, and whether the engine appears to be maintaining the level of power that it does have. Some previous practice of maintaining height with minimum power at your maximum range speed will certainly serve you well.

As a rule of thumb your maximum range speed in still air is more or less your best glide speed, let’s say 60k. If you are flying into wind add about one third of the wind speed; windspeed 20k, so 60+7 = 67k. If flying downwind just maintain best glide speed. Naturally this brings into the question where might be the best divert, if you are bucking a strong headwind it might well be better to turn around and run downwind.

The exercise

On a calm and near cloudless day, get airborne and, at a safe height, set up your standard cruise figures. We are going from the known to the new, and it may help to have a friend along with whom you can analyse and discuss the results, as well as maintain a good lookout while your own head is in the cockpit.

Reduce the power 100rpm, maintain height and retrim as accurately as possible. When settled at this new speed, note the rpm and the resultant reduced speed, plus the slightly higher nose attitude, as this slightly incremental trend will continue.

Reduce the power by a further 100rpm and repeat the process to remain straight and level at the slower speed, and the new marginally higher nose attitude and retrim as accurately as possible to maintain height and heading. Let it settle.

Adjust the elevator trim as best as can be done. Also, check you are in balance with the slip ball, or turn needle – anything out of alignment on the airframe creates drag, so try to eliminate any unnecessary performance loss.

Repeat further reductions in power, using smaller increments as you approach maximum range speed, selecting a new nose attitude and retrim.

Once the appropriate speed is reached, note throttle, trim. Nose attitude and rpm settings for future reference.

Decision time

In a real world situation, if you are fortunate to have a reserve of power when you set up for your best range speed, you might usefully use it to slowly gain some additional height. However, bear in mind that using that additional power might exacerbate whatever the engine problem is. It might be wiser to not overstress the engine any more than is absolutely necessary.

Check the GPS for your ground speed and assess whether you have a headwind or tailwind component. A significant headwind might mean that the best diversion option is downwind or crosswind. If it remains into wind, add the appropriate 1/3 windspeed to your range speed. If you don’t have sufficient power to maintain best range speed, you can slow up the aircraft a bit more but be very wary indeed of getting too close to the stall, if you can’t keep 10kt above stall speed and maintain height, you are probably better off using what power you do have to continue as gentle a descent rate as possible and, if this won’t get you to an airfield, find the best field you can and carry out an off airfield landing.

If, with good fortune and good airmanship, you are able to make it back to an airfield, don’t take any more chances than you need to. Call them early to explain your situation and ask for a priority landing so you can position for the minimum circuit positioning or a straight in, whatever is appropriate. They will be more than happy to help.

A few additional ‘tricks’…

■ Having established the throttle setting for max range, mark it so it can be readily found. ■ Make use of any lift, such as rising air above a motorway on a hot day. ■ If you have a variable pitch propeller, a slightly finer pitch may be of benefit.

Depending on how you handle it, a rough running engine does not have to be the end of a good day. Having thought about the possibility of flying on reduced power, and practiced the exercise, it will at least aid the necessary decision making during such a situation.

Over the years I’ve had possibly more than my share of engine issues in a Stampe, Harvard, Tiger Moth, Grumman AA5A, Monnett Sonerai, Auster, Yak 9, Starduster and a replica Sopwith One and a Half Strutter. I managed to make it back to base on four of those occasions.

Tale of the One and a Half Strutter…

I was part of a loose formation transiting with the Czech Pterodactyls, a display team, on our way from Jihlava to Cambrai in France. I particularly wanted to attend this show as it marked the centenary of the first major tank battle in WWI, and my grandfather had been there. Petr was leading in an SE5a, Franny in his Fokker Dr1 and Petr’s aunt in an Eindecker (apologies that I cannot recall her name, but she used to lead the Red Bull team flying Zlin 50s). I was sitting behind a dummy Vickers machine gun mounted on a padded circular excuse of a windscreen, flying a replica Sopwith One and a Half Strutter. My kit was stored in the rear gunner’s cockpit, he was travelling with the ground grew along with the second Eindecker which would be shot up as a ground target, the replica lorry, which was also to blow up when strafed, the engineers, the armourers and the pyrotechnics crew. It’s quite an explosive exhibition and when I first flew with them, I was actually firing blanks from a pucka machine gun and the cases were ejected into thin air... and was advised not to fly over the crowd when you are shooting! All guns now are gas firing.

Having refuelled and taken off as number four, I detected a slight rattle from somewhere ahead of me as I was cutting the corner to catch the formation up. We were to be transitioning under part of Frankfurt’s airspace and in between the relatively low and very wooded Taurus mountains. Behind the others I played around with throttle, mixture, and carb heat but the oil gauge was telling me all was well… but the slight rattle was definitely getting worse in terms of roughness, decibels and now a bit of a tremouring shake.

I tried calling Petr, without any luck, and none of the others, all still ahead of me, responded either. I could still stay with them but wondered how long things were going to hold together. Our route was starting to weave around the

mountains and there were not many places to put down, so I opened the throttle to draw alongside Petr in his SE5a.

The clattering was getting worse. As I drew into formation Petr must have heard me as he turned to look at me and I faked a pantomime grimace, pointed at my engine and gave a thumbs down. He responded with a perfectly audible RT transmission, the first of the day.

“Clife” (Czechs have trouble with Vs) “Clife, you are losing oil.” Almost matter of factly he pointed behind to a grayish trail of smoke and immediately banked hard right, beckoning for me to follow. We flew down a narrowing valley Below The axle assembly is pretty low slung on the replica Sopwith, and that beet looks rather solid and unforgiving. and two fields came into view, one had a standing crop and the other was green. The poor old girl was given a slight respite as I throttled back in order to ascertain further conditions but, from a more by luck than judgement high base leg, it suddenly went quiet as the prop stopped turning and the poor old Verner radial seized. A bit of a slip and the wheels trundled in between the packed rows of sugar beet.

The others arrived overhead as I got out of the dear old bus that had looked after me and allowed me to get to this remote but safe spot. I was also fortunate in that the low-slung undercarriage axle had just skimmed over the top of a pretty solid crop. Waving their goodbyes, my colleagues continued on their way to Cambrai as I started to wonder what I should do next.

In the next valley, Mannfred was packing his radio control planes away in the boot of his car when he saw what appeared to be a dogfight of four WWI aircraft. They dropped out of sight… and only three reappeared so fortunately for me, he came to investigate. I couldn’t have been in better company with Manfred and his wife, who looked after me until the team returned from a successful Cambrai show and picked me up. Ironically, I missed the Cambrai display and survived, just as my grandad had – he too missed Cambrai as his tank broke down!

The dear old Sopwith is airworthy once again and I am due to meet her again this summer, Covid-19 restrictions permitting. The cause of my woes was an errant valve that, having become detached, proceeded to punch a hole through its piston. If my gunner had been in the rear cockpit he could have warned me when the oil trail started. I told him he could fly with me en route next time but he wasn’t too sure about that suggestion!

Right Didn’t quite make it back. Clive put the stricken Replica Sopwith One and a Half Strutter down in a sugar beet field.

A partial power recollection

By Brian Hope

Some years ago, I was on my way to Berlin in my Jodel with a gaggle of friends. We routed Midden Zeeland for Customs/Immigration and then Damme for an overnight. Damme has good camping facilities, with some cabins for rent if the weather is a bit iffy, and also has a decent restaurant on site. Two or three of the group decided that they would night stop at Osnabrück because it was a larger city and they preferred hotels to tents… strange, but it takes all sorts. The plan was to meet at our final destination, Kyritz, north of Berlin. I’d been to Kyritz before because they held a fly-in there and arranged for small groups to fly into Tempelhof, which I had done previously. Because this famous WWII / Berlin Airlift airfield was scheduled to close fairly imminently, this group trip came about, in fact this was the trip which Martin Ferid came along on and wrote so eloquently about in the January issue.

After a cup of coffee and a sticky bun in Midden Zeeland met slagroom – the rather unfortunate Dutch words for the cake coming with that aerated ‘whipped’ cream from a pressurised can. Compare the delightful French expression avec chantilly or even the Hope family’s, with phut phut, as the stuff was christened by my then teenage little sister decades ago, still retaining that epithet to this day. It is with some relief I guess, that I report she did not however, pursue a career in linguistics. Anyway, cream and cake consumed, we headed off for Damme, or Osnabrück, with me as the lead aircraft.

The route more or less took us east, heading towards Osnabrück, and as we neared the city, those staying there would continue straight on a short distance and join for landing, while the rest of us turned for a more north-easterly heading for about another 20 miles for Damme. Everybody was looking after their own navigation and it was very much a ‘same way, same day’ arrangement, so as we approached the corner we had become pretty well spaced out, in the non-hallucinogenic sense of course.

I had by then turned to listen out on Damme, to see how busy they were, and was surprised to hear one of the group, a friend of a friend and not a regular acquaintance, let’s call him Dick, calling them for landing instructions. I probably had about 25nm to run and, being in a slightly faster aircraft, was rather bemused by this. Anyway, Dick continued his discussions with Damme, made the various return calls and, just as it was getting interesting, my engine went onto three cylinders and started rattling my fillings out.

I throttled back to about 1,900rpm, where it smoothed out to a tolerable level, and I was able to maintain height at a slightly slower speed, but rather than push on to Damme, I decided it would be more prudent to head for a gliding site, Achmer, about 10 miles farther on and only two or three miles east of track. I tried to make contact with Damme, who clearly (unclearly?) were not answering me, so I said to Dick, “When you get down, can you tell Damme that I have an engine problem and am diverting to Achmer. “Yes”, he said, “will do.” And having found a radio frequency for the gliding site, I tried calling them. There was no response, but it was a Thursday, and as in the UK, many airfields and strips only come alive at the weekend. As the airfield came into sight I decided it would be prudent to keep to the probable deadside, given the wind direction, rather than fly overhead, just in case they were winch launching, but with a couple of cars and gliders at the upwind end of the field where there were a number of glider trailers, it was pretty evident the place wasn’t active.

I landed and taxied up to the clubhouse and there was indeed nobody else about, so I whipped off the cowling, felt for the cold cylinder – C90 owners will not be surprised that it was the portside front. I took the rocker box cover off, tapped the compressed exhaust valve and it sprang closed. Rocker box and cowling back on, it ran sweet, so I took off, probably no more than 20 minutes after I’d landed, and continued on to Damme who, along with my mates who had by then landed, were getting a little concerned about my non arrival. Dick wasn’t there either. In retrospect I should have called Damme or one of the group before I departed Achmer, but I called Damme once I was airborne as it was by then well in range.

Above The Airlift Memorial at Templehof commemorates the 39 British, 31 American and 13 Germans who lost their lives during the Airlift, which operated from June 1948 until September 1949. In total 266,600 flights were carried out, moving 2,325,809 tons of fuel, food and general supplies. They were flown in to Templehof, Gatow and Tegal, the later being built by Army Engineers in less than two months.

Valve problem

Next day we headed off for the 1hr 40mins flight to Kyritz and, as the airfield hove into sight, I was contenting myself that the valve problem had been a temporary issue. I was just entering the circuit when the engine went onto three again and, before I’d even limped to parking, I had decided that the pot had to come off before heading for home. I wasn’t keen on heading out over the Channel on the homeward trip if there was a chance of it happening again.

After the usual hearty welcome from Hubert Eckl, the ever ebullient organiser of the event, I explained my predicament and he very kindly borrowed the requisite cylinder base spanners and torque wrench from the local maintenance outfit (they didn’t operate over the weekend). Between our group, we had everything else we needed or could borrow from the gliding club, who very kindly allowed us to use their workshop. I rang my inspector, and he was happy for me to do the work, so we set to, being careful not to damage the rubber sealing ring that fits around the base of the cylinder as we did not

have a replacement. I’m a fan of the ‘no-blow’ exhaust gaskets, and they too are reusable. We had the cylinder off before lunch and, as expected, a fragment of carbon had wedged between the valve stem and the guide. We cleaned everything up, making sure the valve action was perfectly free and smooth, and had the cylinder back on by late afternoon. We finished the odds and ends the next day in between the activities – I flew into Templehof with one of the others; having been in with the Jodel the year before it wasn’t too much of a disappointment. When we got back we finished things off, I flew a quick couple of circuits and gave it another good check for leaks etc., and I was all set for the trip home the next day. And Dick? Well needless to say he had landed at Osnabrück and when he saw one of the others who’d landed there said, “I thought you guys were going to Osnabrück.” He didn’t mention that I had an engine problem and was diverting to Achmer until they were at dinner later that evening, so it was just as well I wasn’t upside down in a field somewhere...

It was a classic case of him hearing the two destination airfield ICAO codes being mentioned and plugging the wrong one into his GPS. No chart, no plog, just follow the magenta brick road, although Below Field repair. Refitting the cylinder having resolved the sticking exhaust valve issue. Rally goers may recognise the chap in orange, Volke Teske, who was an attendee for many years in his Jodel. back then it would only have been a grey arrow on a GPS.

He also happened to be in the group of six aircraft that I was in on the way in to Templehof, which was in a serious area of controlled airspace as the then main Berlin commercial airfield, Tegal Otto Lilienthal was very close, more or less on the other side of the city. There was a dedicated route in, with appropriate reporting points, one of which was a couple of miles south of the airfield, around which you had to carry out a holding pattern if there was IFR traffic inbound – which there just happened to be as we approached it.

The plan was that the lead aircraft, with a German pilot on board, was to handle the radio and the rest of us maintained a listening watch and ‘follow the leader’ as instructed. When we were told to hold, Dick, who clearly hadn’t read and/or understood the brief, interrupted ATC and told them he didn’t understand where to hold and was continuing to join right base. Fortunately, the IFR traffic, a light twin, was down before he called final, and they simply told him to continue to final and then cleared him to land.

Surprisingly, nothing else was said about it but, maybe not so surprisingly, he never came on a trip with us again… ■