Photo Report – Banner Towing Above Zagreb, Feb 2008

By me
All photos me too, copyrighted as usual

Looking back through all the articles I’ve posted here, I saw I’d made quite a few boastful promises about topics that in the end never materialized :). So, still waiting for something to happen here in the present, I’ve decided to clear my topic backlog, starting of with my first true air-to-air photo experience – banner towing :).

1. Fly-by-wire

While banner towing in flight seems – and is – a pretty straightforward affair, down on the ground, getting the thing airborne, is a different story altogether. Despite popular myth, taking off with the banner attached causes more problems than it solves, particularly on uneven grass runways such as at Lučko – where it would promptly be torn off and shredded, not to mention all the adverse effects it would cause for the unlucky towplane.

To get around this problem, somebody somewhere at some point had borrowed a WW2 method – why not snag the banner inflight? To quote Jeremy Clarkson of Top Gear, “How hard can it be?” :D. The idea is that the banner’s tow cable is suspended between two poles at some height above ground, usually about 2-3 meters. The towplane would then, trailing a hook on another cable, come down low and snag the banner, lifting it off the ground as it climbs away. Those of you who have seen images of Dakotas picking up troop transport gliders during WW2 will immediately see the similarities.

A visual illustration as 9A-DMJ goes down for a snag. Note also the hook cable attachment assembly at the base of the tail. Sorry for poor quality, but for the life of me I can’t find the original, so I had to take this one of my Facebook photo gallery 🙂
9A-DDD going down for the pickup. The approach is usually flown at about 70 knots and 10 degrees of flaps in the Skyhawk. The speed has to kept at around that figure – any faster and the sudden drag and inertia of the banner will stress the airframe unnecessarily, while any slower means that when the banner yank does come, it can pull the aircraft very near the stall (with the added complication of the engine run-up delay at low throttle settings)
During taxi and takeoff, the hook end of the cable is carried in the cabin by the second crew member. Once airborne, the hook is lowered into the airstream until all the slack in the cable is picked up
A frontal view on a recent mission
Side view. Note the reinforced cable mid-section that acts as a sort of bungee to absorb some of the forces and inertia during pickup
A nice and clean hook up. Sometimes the hook and banner cables can tangle up, with the banner towed not by the hook, but by the tangled cables. This can be quite problematic if the knot untangles in flight – the banner then freely falling away – the reason for which there is always a “ground spotter” with a radio station observing the pickup. If the cables tangle up, the SOP is to jettison the entire thing and start over
Banner snagging being pretty much a visual art, it is not uncommon to miss the banner cable altogether (by anything from inches to meters). In this case a go-around is executed for another attempt

After a successful snag and climb away, the rest of the flight becomes routine – with careful monitoring of the engine temperature gauges that is. Despite most banners weighing not more than 20-ish kilograms altogether, their large surface area creates a lot of drag. This necessitates a higher throttle setting and if not flying fast enough for sufficient engine cooling, it’s not really that difficult to overtemp the engine.

With the mission completed, the banner is then dropped from the aircraft during a slow, low pass. The release itself depends on the hook and tow mechanism, but in our case the whole cable – all the way from the attachment hook below the tail – is jettisoned, to be untangled and separated on the ground. This leaves the aircraft free to perform a normal, unencumbured landing.

Note that the entire cable is released, with only the fixed tail hook remaining in place. For many pilots, hitting an exact bull’s eye with the cable is almost a sport 🙂

2. A skiing competition, a casino and some fog

While all of the above is fine and dandy, back in the winter of 2008 my aeroclub had gotten a bit ambitious :). The mission was to tow the largest banner ever towed in Croatia, measuring 5 x 30-something meters. Doesn’t sound like much the first time you hear it, but in effect that’s a 150 square meter airbrake – more than three times the surface area of my apartment!

The venue was the Snow Queen skiing competition held on the northern slopes of the Medvednica mountain between 15. and 17. February 2008. And the customer – a large casino near Šentilj, on the border between Slovenia and Austria. Connection – I see none, but it didn’t matter since it got us up in the air with no questions asked :).

Fortunately for our towplane, the temperatures had plummeted during the weekend, down to around -15 Centigrade at the altitude at which we had expected to do our run. (round 2,000 ft) With such a draggy mass behind it, and the requirement to fly at 70-75 knots so people on the ground could actually read what was being towed, engine cooling was a serious issue, so the lower the outside temp, the better.

Now, the original plan was to do a run on the 15th, with DMJ acting as the towplane and DMM – with me on board – acting as the photo ship to immortalize the whole event :). However, even before leaving the ground we had run into a small problem…

Going up! As you can see, the weather was, for our intents and purposes, crap. It was still okay here in the open, but north of Medvednica – where the wind kept blowing moisture up the slope – it was downright awful
Rounding Medvednica from the west near Zaprešić. As you can see, the weather was steadily deteriorating, but undaunted we went ahead to see what’s what 🙂
In an ironic twist, our 100 HP Cessna 150 turned out to be faster than the 210 HP Reims Rocket, so we had to orbit around a bit to let DMJ gain some distance before our photo run 🙂
Lining up for another run, showing just how large that banner actually was :). While weighing just under 20 kilograms, its sheer area caused so much drag that DMJ – lightened, with half-full tanks and one person on board – needed to be run at near maximum continuous power
Closeup of DMJ while skirting the northern slopes of Medvednica. The visibility was still good compared to what we hit a few minutes later…

Pretty soon however we ran into problem #2. The ski track which we were supposed to fly over – a track very popular with local skiers – is quite narrow and tucked away between two mountain crests. To follow it, we’d have to fly up the through, climbing continuously, in formation and poor visibility, with one aircraft that was underpowered and another that was barely hauling itself as it was. Realizing conclusively that it would all end in a pretty big accident, we turned round and scurried back toward Zagreb, to try and at least save some of the mission there.

Following one of the city’s fast peripheral roads, with visibility mercifully increasing
Keeping low above town. Though the minimum altitude for flyovers is 2,000 ft – about 1,600 AGL – during banner-towing missions this can be lowered by approval. We may have taken that a bit too seriously… 🙂
A wide view of the historic city center, with the Cathedral and old Kaptol fortifications easily identifiable

So far so good as far as the towing was concerned, but my photo session was turning into a bit of a mess. The poor visibility and light, coupled with the turbulent downdraft from the mountain, meant I couldn’t really do much with my unstabilized telephoto lens, so to conserve fuel, we turned for home, leaving DMJ to fly two more short runs above town.

3. Cold, cold, cold!

While the results of the first run were mildly disappointing to say the least, the designated god of aviation – Murphy 😀 – allowed us to make it all up on the 17th, when the weather finally cleared. Beautifully clear skies, still air, visibility one can only hope for and an even lower temperature were just too good to pass up, so we  saddled up and full of optimism decided to give it another shot…

A spirited low-level departure above the field to kick off an excellent mission!
Now this is more like it! 🙂 Shot with the window open – and -17 C outside – with a wide angle to give an impression of size and distance
What a beautiful setting for a photo shoot! Looking north above the northern foothills of Medvednica, with the track right behind us

Because the shoot was going so well, Mr. Murphy decided to intervene again and as we neared the ski track, our coordination sort of broke down :). The problem was that to get good shots, we had to fly to the left, above and somewhat in front of DMJ. This meant that my photopilot couldn’t see DMJ because I was in the way, DMJ couldn’t see us because it’s wing was in the way, and the need to maneuver around hills and keep station above the track meant that our graceful aerial ballet quickly degenerated into a left-footed cha-cha-cha as we tried to keep our little formation together.

My favorite shot of the day, just as DMJ is about to pass below us – without actually seeing us until we were right on top of it 😀
A beautiful day, the throaty roar of the engine, and playing catch above the mountaintops. Can it get any better than this? 🙂

With my hands trembling and my skin cracked from the cold – -17 C at 70 knots in propwash without gloves, absolute genius on my part – and our mission completed (relatively, given there were few spectators out :D), we set course for home. As before, DMJ went to do a circuit of the town, while we proceeded directly to Lučko, so I could catch a shot from the ground as well 🙂 (I was having a photo field day).

Turning final for RWY 10 after one of my best photo experiences to date 🙂
DMJ inbound for release. The angle exaggerates the size of the banner, but it looks cool 🙂

Unfortunately, getting some “inside” photos from the towplane is a bit difficult and impractical – mostly because both crew are busy with other things… and there’s honestly not much to see; most of the time the banner itself is outside the the crew’s field of view, so it pretty much looks far better from the outside :). I’m also hoping to get a good, systematic sequence of the pickup, but that will have to wait for some warmer weather… 🙂

Photo Dossier – Piper PA-18-150 Super Cub, 9A-XLJ/9A-DLJ

By Boran Pivčić
All photos author

It’s about time I got to grips with this little aircraft here. Despite outwardly being just a normal Super Cub, this specific little machine has a very interesting story behind it. It was assembled by hand by Mr. Vlaho Ljubić, who spent six years working on it – literally from the ground up, when it was still a random collection of bolts and structural components.

The aircraft is basically a stock PA-18-150 without any modifications, the only difference being the instrument panel layout – but that varied between batches in factory-built models, so we can’t hold that against it :). It is painted in a scheme taken off the Cub Crafters CC18 replica of the Super Cub, but in lighter tones (the original scheme can be seen here: http://www.airliners.net/photo/CC18-180/1423224/L/). Its first post-assembly fight was on October 12th, 2008., on a lovely warm and calm afternoon. The following pictures go out to Mr. Ljubić, who generously allowed me to crawl over every inch of the plane :).

(an additional note about the reg – initially, the aircraft was registered as 9A-XLJ, X being the prefix for the experimental register. However, being in essence a stock, factory design – and given that the whole experimental thing is still wobbly in Croatia – it was transferred to the standard GA register – prefixes B, C (rarely) and D – becoming 9A-DLJ)

Shining nicely in the autumn sun a couple of days before its first flight
Shining nicely in the autumn sun a couple of days before its first flight
Like all Cubs - Super or otherwise - this one is mostly fabric covered, with a metal frame structure underneath. The resulting decrease in weight compared to traditional aluminium structures offsets the need of periodically replacing the fabric
Like all Cubs - Super or otherwise - this one is mostly fabric covered, with a metal frame structure underneath. The resulting decrease in weight compared to traditional aluminium structures offsets the need of periodically replacing the fabric
The aforementioned panel. Simple and uncluttered, it contains all you really need for VFR flying.
The aforementioned panel. Simple and uncluttered, it contains all you really need for VFR flying.
Final engine inspection before its first post-assembly flight. Like the majority of all Super Cubs, this one has the O-320 150 HP engine which does wonders for an aircraft as light as this. Some Super Cubs have smaller 95 and 105 HP engines, while a few - mostly glider-towing ones operating at higher altitudes - have been modified with up to 180 HP.
Final engine inspection before its first post-assembly flight. Like the majority of all Super Cubs, this one has the O-320 150 HP engine which does wonders for an aircraft as light as this. Some Super Cubs have smaller 95 and 105 HP engines, while a few - mostly glider-towing ones operating at higher altitudes - have been modified with up to 180 HP.
Revving up the engine for a running check. Thankfully for me, the brakes were working perfectly :).
Revving up the engine for a running check. Thankfully for me, the brakes were working perfectly :).
Taxiing out for its first flight!
Taxiing out for its first flight!
Go little Cub, go!
Go little Cub, go!
Trundling by at 70 knots while high overhead something zips by at 500+ :)
Trundling by at 70 knots while high overhead something zips by at 500+ 🙂
Taxiing in back home. The smile says it all!
Taxiing in back home. The smile says it all!
Banking left, banking left! :) An air-to-air session on the aircraft's fourth flight (I think). 9A-DMI served as my trusty photo ship once more
Banking left, banking left! 🙂 An air-to-air session on the aircraft's fourth flight (I think). 9A-DMI served as my trusty photo ship once more
Approaching to form off our right wing above the city of Zagreb
Approaching to form off our right wing above the city of Zagreb
Sliding in alongside and looking beautiful!
Sliding in alongside and looking beautiful!
Going shopping. Diving away from us above King's Cross, one of the largest shopping centers in Zagreb
Going shopping. Diving away from us above King's Cross, one of the largest shopping centers in Zagreb
Cooling down in the afternoon
Cooling down in the afternoon

VFR Trip Report slash Air To Air Session – Trakošćan Castle, 22.06.2008.

By Boran Pivčić
All photos author

When you get invited to participate in an airshow, you usually don’t ask too many questions. When you’re asked to participate in one in formation with two other aircraft, you don’t ask any, but promptly kick the tires and light the fires :).

Back in the summer of ’08 (not ’69), the aeroclub I’m part of was asked whether we’d have any objections to flying a short display at an aviation happening near Trakošćan castle in northern Cro. There were none of course, but – in line with the above – to this day I have no idea what it was we were asked to fly over. But there was flying and photography afoot, so I was there, no questions asked.

1. The aircraft

Our formation was to consist of two Cessna 150Ms mismatched with a Reims FR172F Rocket sporting more power than the two 150s combined. To add to the difficulties, it was +37 outside and my photo ship just had a new engine installed, which meant we couldn’t floor it as much as we would have liked. But undaunted, we got down to preparing, making up a plan as we went along.

Registration: 9A-DMJ (ECOS Pilot School)
Type: Reims FR172F Rocket
Mfd: 1970.
Engine: Continental IO-360, 6-cylinder, normally aspirated @ 210 HP, driving a three-blade constant speed prop

Registration: 9A-DMM (ECOS Pilot School)
Type: Cessna 150M
Mfd: 1975.
Engine: Continental O-200, 4-cylinder, normally aspirated @ 100 HP, driving a two-blade fixed pitch prop

Registration: 9A-DMI (private)
Type: Cessna 150M
Mfd: 1976.
Engine: Continental O-200, 4-cylinder, normally aspirated @ 100 HP, driving a two-blade fixed pitch prop

DMI was to be my photo ship, while DMM was nominated as the lead aircraft – being the slowest of the remaining two and dictating the pace.

2. The flight

With takeoff being scheduled broadly around 12:30, I arrived at the field about an hour earlier, hoping to make myself useful and help prepare the planes for the epic 45 minute flight. While DMJ sat ready and waiting, DMM was getting a wash – though I don’t know whether it actually needed it, or the guys were looking for a fun way to cool down on one of the hottest days of the month.

A bottle of Arf wipes away all your troubles :)
A bottle of Arf wipes away all your troubles 🙂

Once fresh & clean, we got down to the serious business of checking the bird out before the flight. As a regular maintenance check had been done a couple of days prior, we were mostly left with the preflight check and throwing out everything not necessary for the flight to save weight. After briefly thinking about losing the seats, we settled for more conventional stuff like emptying the baggage hold of various miscellaneous stuff, boxes, tiedown cables, oil canisters and the like.

With the weight-saving measures completed, we settled back and waited for everybody to assemble. The impromptu crew roster required six members, two young PPL pilots and two instructors in DMM and DMJ, and my photopilot and me in DMI. Wanting to blunt DMJ’s power advantage, we found two more willing PPLs who were to be the ballast in the back.

Finally ready, we fired up our engines at around 12:20 and taxied out to RWY 28. The plan was for all three of us to take off in formation: DMJ from the front, (since it could out-accelerate the 150s) and DMM and DMI in the back. However, the tight apron of the club – and a momentary breakdown in coordination – meant that at the RWY 28 threshold the 150s ended up first, with DMJ bringing up the rear. As there was quite a lot of traffic at that time, we decided not to complicate things any further and taxied out onto the runway as it was.

Lined up, about to start our takeoff run...
Lined up, about to start our takeoff run...

Flooring the throttles – not an impressive spectacle at +37 Centigrade – we took of in pair with DMM, while DMJ started rolling about 30 seconds later. Once airborne – barely – we spread out a bit and turned toward the town of Zaprešić some 6 km away.

Our route took us:

N point (Zaprešić, CTR Lučko exit point) – Krapina – Trakošćan – Krapina – N point

a route all of us knew well from our student days. Navigation on this bit is very easy and boils down to simply following the Zagreb – Macelj highway which runs up almost to the castle itself. Being in formation, we kept our heads down at around 1,500 ft, giving us a 1,000 feet of terrain clearance most of the way.

Trying to close our formation while climbing toward Zaprešić
Trying to close our formation while climbing toward Zaprešić

We actually made it halfway to Zaprešić before the first problems started  to appear. Careful not to force DMI’s new engine, my photopilot Ivan kept it at a maximum 2400 RPM, 200 short of its declared maximum. Doesn’t sound like much, but on aircraft with fixed pitch propellers most of the real power is found in the top 100s. Consequently, with a climb speed of barely 200 fpm, we started falling behind. Mind you, with a temperature of 35 C at this level, DMM wasn’t doing much better either, while our measures for levelling the playing field didn’t seem to be working, as DMJ had to throttle back in order to keep up with us.

However, a couple of kilometers downrange we finally reached our 1,500 ft and set about trying to fall into a proper formation for some photo ops. Once out of the climb, DMI picked up speed and we soon caught up with DMM.

Closing up, though still a bit too far apart...
Closing up, though still a bit too far apart...

Eventually – after some coming and going – all three of us were holding something resembling a stable formation. As DMM and DMJ tightened together for their photo shoot, we in DMI crawled ahead and a bit up to give me a clear view, away from the wing struts and landing gear.

Our two canaries holding a nice, not-too-tight formation above the hilly Croatian countryside
Our two canaries holding a nice, not-too-tight formation above the hilly Croatian countryside
DMJ banking right for a livelier photo...
DMJ banking right for a livelier photo...
Adding a few tens of feet for a different viewpoint
Adding a few tens of feet for a different viewpoint

I must admit this was quite enjoyable, shooting through the open window. Last time I did that four months earlier, it was -15 outside and the experience was not quite so pleasant (more on that in one later post). With the big fan up front throwing some welcome fresh air into the cabin, we actually left the window up most of the way.

After having my fun, we tightened back together, as the terrain was getting progressively hillier. The leg from Zaprešić to Krapina takes just under 20 minutes and ends in some 3,000 ft high mountains, so with a good 10-15 minutes gone, we needed to start actually flying, not just joking around. The approach to Trakošćan isn’t all that easy, so now was the time to coordinate. Meanwhile, between transmissions on my handheld radio station, I snapped a few additional photos.

To quote Jeremy Clarkson of Top Gear: "Aww look, it's clouding over" :)
To quote Jeremy Clarkson of Top Gear: "Aww look, it's clouding over" 🙂

Soon enough, we were nearing the mountain Ivanščica, right around Krapina. To jump over its lowest part, we needed to climb another 1,000 ft, which – given our appaling climb performance earlier – required some forethought.

Climbing gently in a very loose formation to give us some maneuvering space in case our climb petered out...
Climbing gently in a very loose formation to give us some maneuvering space in case our climb petered out...

Trakošćan itself is surrounded by the foothills of Ivanščica, so we needed to be very careful. More than once, DMM and DMI had to take a slight detour around a peak because we judged our climb rate wasn’t going to get us over it in time. DMJ, bless her six cyl engine and constant speed prop, had no such problems.

Tailgating each other round the side of the mountain after our first pass over the castle. DMM was in the lead again (the spot to the right of the picture), DMJ was second and we were bringing up the rear to photograph the whole event
Tailgating each other round the side of the mountain after our first pass over the castle. DMM was in the lead again (the spot to the right of the picture), DMJ was second and we were bringing up the rear to photograph the whole event

When we finally crossed the hills, found the castle and positioned ourselves, we broke into what could maybe be described as a line-astern formation, chasing each other toward the castle grounds. Our plan – drawn up with the organizers – was to make a series of low passes, trying to nail one in formation. However, the restrictive terrain around meant we had to go at it alone, so we floored all three planes and dove gently toward the valley floor.

Shot from a slight bank on our first high pass. Don't know what was going on down there, but I spotted a number of Red Bull flags and two helicopters, a private Robinson R-44 Clipper II and an airforce Mil Mi-171Sh, seen here to the bottom left
Shot from a slight bank on our first high pass. Don't know what was going on down there, but I spotted a number of Red Bull flags and two helicopters, a private Robinson R-44 Clipper II and an airforce Mil Mi-171Sh, seen here to the bottom left
Breaking left for another, lower pass. Didn't photograph many of them, was too busy enjoying myself :)
Breaking left for another, lower pass. Didn't photograph many of them, was too busy enjoying myself 🙂
Going down low, following DMJ's example
Going down low, following DMJ's example

After the first high pass, we made several more, each lower than the last. Given the aforementioned terrain around the castle – and the heat – we thought it best not to fool around, so we didn’t attempt the formation one.

Strafing the castle...
Strafing the castle...

With four passes completed and our job done, we turned for home and flew back the way we came in, in pretty much the same wide formation, since the hills hadn’t moved appreciably in the mean time.

By now it was around 1 PM and the sun was sliding to the west. Because the Zaprešić-Krapina-Zaprešić leg runs pretty much north-south, I would now have to shoot into the sun, which I presumed wouldn’t give me many photo opportunities – but the forming up delay on the way out meant I was willing to try at least and end the day with a lot of good photos.

A normal formation at last!
A normal formation at last!
A nice contrast...
A nice contrast...

This time we chose to fly higher, at around 2,000 ft. Because all our photo ops were done, we flew most of the way to Zaprešić in a clean, tight formation, giving everybody a chance to practice holding station off each other’s wing.

DMI taking the lead for a sec, leaving DMM in it's... wake?
DMI taking the lead for a sec, leaving DMM in it's... wake?
All nice and clean and shiny :)
All nice and clean and shiny 🙂

But, in a fit of playfulness, a few miles before Zaprešić our formation finally broke up for good and turned into an all out race to Lučko. DMJ, having 110 unfair advantages, quickly pulled ahead, while DMM fell a couple of hundred meters behind us, despite our 200 RPM handicap. Apart from being quite good fun, it also served to separate and sequence us for landing, so we wouldn’t come in all bunched up.

Wide view of the countryside on the way back. The mountain to the left is Medvednica, at whose feet lies the city of Zagreb. Right off its right slope is Zaprešić, with the Zagreb-Macelj highway showing the way below
Wide view of the countryside on the way back. The mountain to the left is Medvednica, at whose feet lies the city of Zagreb. Right off its right slope is Zaprešić, with the Zagreb-Macelj highway below pointing the way

Passing Zaprešić, we were still a few minutes out from Lučko, so we coordinated our landing sequence via radio. The crew of Juliet, already far ahead, decided to continue  on a panorama flight above Zagreb, leaving us in DMI as number one. Since the wind was calm and there was no more traffic in the circuit, we chose RWY 10 and slid into left base over castle Kerestinec, a convenient turn point.

On final for RWY 10
On final for RWY 10

Landing just after the threshold, we hit the brakes and pulled off to the side so DMM, close behind us, could land. Gunning the throttle to not get stuck in the grass on the taxiway, we rolled of to the ECOS apron at the other side of the field and shut the birds down.

Total flight time: 1h 5 minutes