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Do you know about side-step approaches ? The concept is easy to understand: it starts with a standard approach to a given runway, at least until breaking below the clouds base. Then comes the funny part: a short segment to be flow visually, to line-up with and land on a different runway. No guidance, no auto-pilot, just manual, visual flying, at low altitude, and land.

Such procedures exist at several airports with parallel or nearly parallel runways. Apart from being fun and entertaining for pilots, they allow for a better traffic flow management. Typically, if a landing aircraft is slow to vacate the runway, and the second runway is available, the next aircraft can make the side-step, and avoid a go-around - which is much less fun to fly than a side-step.

Side-step approaches have also be in use at Zurich airport for years. Most landings take place on runway 14, and most departures on 28. The third runway, 16, has a 20 degrees offset with 14, but crosses 28 so both can’t be used simultaneously. However, all planes landing on 14 have to cross 28 during taxi.

To make things easier, ATC offered ILS 14 approach with side-step landing to 16, as long as there is no take-off on 28, thus simplifying the taxi procedures. I experienced it a couple of, time as passenger, and I have to say that it’s pretty impressive, particularly for those seated on the right side of the plane (the side-step is a right turn).

This procedure is not longer used in Zurich, after a couple of incidents where bad coordination resulted in loss separation minima. No collision, but planes taking-off flying low over the landing ones. Not good. Click here to read the investigation report about one of these incidents.

I selected three videos from YouTube to show you how funny these approaches are to fly. I did not found any filmed in Zurich. The first one is at Denver, at dusk, in a rather slow plane, flying a side-step to the right.

That one is slightly more… aggressive.

This one in Vienna is even more impressive, as it includes a very long low-level segment over the approach runway, and then a left turn to the landing runway.

Is not that cool ?

This is the second post in a series about preparing an IFR flight, which I will hopefully do this summer, when visiting friends in England. It will be a Bornemouth - Guernsey leg, and today I’ll give more details about the approach.

In many respects, the ILS approaches to Guernsey are typical, school-like ones. No exotic or special procedures, but many details that must be looked at. For each approach direction (09 - 27), there is an ILS, a VOR-DME and an NDB approach, which follow the same principles.

The approaches start overhead the VOR (or the NDB in case of NDB approach), and start with an outbound leg. Then comes a 45°/180° track reversal procedure to intercept the final approach track.

There is no mandatory holding, but for runway 27, the holding published over the VOR can be used for track reversal, as the turn to the outbound track when coming from the airway would be too steep. I don’t know how likely it is to get vectors to final approach, so I get ready for the full procedure, just in case…

The go-around is always the same as well: fly straight ahead to 2.5, 2.7 or 3.0 miles, depending on runway and approach type, then turn right back to the VOR / NDB and hold. There are also altitude conditions associated with the turn.

That’s for the big picture, now come all the details. At first, both ILS use the same frequency: 108.1. It’s always important to identify beacons using the morse call-sign, to make sure they’re not failed, or undergoing maintenance, but in that case, it’s even more imporant. If for any reason the wrong ILS is in service, this could lead to false indications.

Reading the notes on the approach plates can take time, and it’s better to do that before the flight. One mentions that aircraft unable to receive DME shall advise ATC, and will be given radar ranges at key points of the procedure. I don’t know the reason for that, may be it is because the approach is flown relatively low, at 2′000 feet over the sea, making DME reception less reliable.

The procedure starts at 2′000 feet over the VOR / NDB, and the outbound leg is 7.2 miles long, all at 2′000 feet, so there is no descent planning issue. If starting the approach directly from the airway, at an higher altitude, the standard descente rate of 300 feet / miles means one must not cross the VOR at altitudes above 4′000 feet.

The Decision Altitude (DA) when flying the ILS is at 503 feet AMSL, corresponding to the standard category I 200 feet AGL minimum. The glide slope is also a standard one, descending at 3°.

In case the DME is failed, times are published for the procedure turn, and the missed approach point is then the VOR itself, with obviously a much higher minimum.

Circlings are not forbidden, but there are some prescriptions regarding altitude and tracks. The probability of flying a circling seems very remote, as three different approach types (ILS, VOR, NDB) are available for each runway direction.

After all that preparation, I feel more comfortable with the approach. I will obviously brief the one we’ll fly before executing it, but without a careful pre-study, that would be hard. Any of your tips are also welcome.

If you liked this post, you can read the previous on in the series, about preparing the route from Bournemouth to Guernsey.

Have you already heard of GBAS and Point Merge ? If not, have a look at the latest issue of the Eurocontrol Experimental (EEC) Newsletter.

GBAS stands for Ground Based Augmentation System. GPS is not precise enough to fly an approach to minimums, particularly in the vertical plane, mostly because of atmospheric perturbations. The “Augmentation” consists in sending a correction signal from a ground station, assuming the atmospheric perturbation is the same in a relatively wide area around the airport.

This particularly means that once and airport is equipped, GBAS approaches become possible to any runway, at the cost of a single transmitter. No more need for one ILS per runway, nor for the associated maintenance costs.

A GBAS installation makes possible to fly precision approaches to any runway in range. Precision and low cost. Wow. So why is not GBAS used everywhere ? Because publishing new procedures and fitting receivers in aircrafts costs a lot of money.

Validation of a new system’s safety is also hard task, especially when it relates to guidance in the final phases of approach, where any problem can result in a controlled flight into terrain (a.k.a. CFIT - a.k.a. crash).

The paper from the EEC focuses on interoperability assessment, to see how GBAS approaches can fit in the real world, and it seems quite promising.

The links in this newsletter include a video taken from a plane approaching runway 27 in Egelsbach, with a duplication of the “instruments” displayed for the pilot. The NAV and GS flags appear a couple of time, probably because of lost signal.

This probably seems bad to any IFR pilot, but one must keep an important detail in mind. Egelsbach is not GBAS equipped ! This test flight was based on a GBAS transmitter located 10 kilometers away, in Frankurft am Main Airport… Not so bad for an experiment.