Aviation Topic of the Week
By Michael Oxner, November 23, 2003


Introduction
Previous Week's Topic
Following Week's Topic
Aviation in Canada Blog
Archives

This week's topic:
Airport Operations Part 4: Helicopters

I decided to separate Helicopter Operations into its topic, although you'll see there isn't really a lot to them. There is information in here for both pilots and ATC, just as with the other pages in this series. Let's get right down to business.

Circuit Operations
    ATC and Helicopters in the Circuit
    Autorotation Practice
Take-Off and Landing Clearances
    Runways and Taxiways
    Helipads
    Aprons and "Green Areas"
Surface Movements
    Ground Taxi
    Air Taxi and Hover Taxi
    ATC and Ground Movements
ADDENDUM

Circuit Operations

Airport Operations Part 3b handled circuit operations for fixed-wing aircraft. For the rotorheads among us, it also handled circuit operations for helos, too. The same procedures are used for helicopters looking for circuits as for Cessnas and Pipers and everything else in the air. The entries and the pattern are all common, whether your wings are going faster than you are or not. The one difference that is commonly found for helos is the altitude. Many airports will have special instructions published, and most often refer to altitudes to be flown by choppers in the circuit. 12 Wing Shearwater (CYAW), in Nova Scotia, has a normal circuit altitude of 1,200 feet, based on its elevation of just under 200 ASL. They actually break down circuit operations like this:
Anyone can see the reason these were established is to keep aircraft in different speed ranges at different altitudes. In any case, anything other than the standard for operations at a specific airport is normally found in the PRO section of the airport's entry in the Canada Flight Supplement.

ATC and Helicopters in the Circuit

Controlling helicopters is a funny thing for instructors and ATC trainees. All too often the new trainee will be uncertain of what to do with a helo, and sometimes make a spectacle of himself while attempting to issue instructions. Helicopters are really easy to work with. They are able to stop for you in the air, if needed, they're so flexible. They aren't likely to want to, but they could. Forward speed is always good in case of an engine failure requiring an autorotation (see below). Basically, helicopters are your most flexible client. They can reduce their speeds, if necessary, to that well below conventional aircraft. They can fly at speeds comparable to other aircraft in the circuit (unless all your circuit traffic happens to be F-14s doing overhead breaks) but the best part is that they rarely want to fly an approach to landing in the circuit and generally want to come straight in to the field and land somewhere, thereby staying out of your traffic circuit altogether. All you need to do is get them through a hole in your traffic line and they'll land without having to be mixed in with the rest of them. "Proceed directly to Apron III, not above 1,000 feet. Traffic is a C172 in downwind at 1,500"

Autorotation Practice

Just as important as engine failure and forced landing handling is to pilot training for fixed-wing aircraft, "autorotation" practice is important to helicopter pilot training. In the event that the engine (or more than one in the event of a multi-engine helo) fails in flight, the helicopter is capable of continuing a controlled descent to a safe landing. The rotors have a fair amount of inertia in them when they are swinging around, and the airflow through the rotor disc will, if handled right, actually keep the rotors spinning. This is the whole principle of how gyrocopters, or autogyros, actually fly to begin with. The wind spins the rotors, allowing forward flight. The idea in a helicopter is to control the descent as much as possible without using the collective control until the final stages of the approach, and then flare the aircraft just over the ground to cushion the landing. Forward speed is used in this type of approach, so expect a helicopter practicing these to continue forward instead of dropping straight down from where he is.

Many helicopters without wheels would much rather do these in a field, and may even want to do so at the airport beside or between runways. Treat them just like any other aircraft in the approach sequence. The one thing that differs is that technically, the infield between taxiways and such generally isn't considered part of the manoeuvring area (unless specifically designated by airport authorities), and is uncontrolled. As such, ATC shouldn't issue landing clearance (or take-off clearance when he's ready for another go at it). A term often heard would be something like, "land at your discretion," to remind the pilot that he's on his own hook out there. Having said that, certain airports may operate differently, especially those where helicopter training operations are common. If in doubt and if it's a concern, ask ATC. See below for more information.

Take-Off and Landing Clearances

If a helicopter is departing from a runway, take-off and landing clearances may be issued as per normal. At many airports, taxiways are routinely used as runways for helicopters, particularly larger ones. This provides for a good supporting surface in the event of a failure in the early stages of flight. For IFR flight, obstacle clearance is normally only assessed from runways at airports, and for this reason, IFR helos will normally depart from runways.

A large number of helicopter operations take place on Helipads. The helicopter equivalent of a runway for planes, these are typically prepared and marked, and often have a windsock nearby. Many have lighting. A large number of hospitals, office buildings and even harbour wharfs have helipads. If the helipad is on the manoeuvring area of an airport, then take-off and landing clearances are issued to these in the normal fashion. Quite often, helipads in the controlled surfaces of airports are located on taxiways. If you're controlling TWR and GND is staffed, make sure the two of you coordinate helicopter take-offs and landings to ensure that nobody is taxied onto a helipad or taxiway being used as one while a chopper is in motion. Clearly state, "taxiway A is yours", or "the south pad is yours" as a GND controller, and clearly state the return of the surface to GND's control if you're the TWR controller.

In many cases, helicopters will want to land exactly where they want to park. This will often have them landing on designated sections of airport aprons, which include private aprons. ATC MANOPS 353.1 tells us that we are only to issue take-off and landing clearance provided the operation takes place on the manoeuvring area. As defined in a previous topic, this includes taxiways and runways. Since aprons are not considered part of the manoeuvring area, they are not actually controlled. What difference does this make? Well, from an ATC point of view, how can you issue a clearance for an operation if you don't have the authority to keep others out of the way? Because of this, the TWR controller will normally issue winds, traffic information, and instructions to be followed once getting airborne, and then say something to the effect of, "depart the (FBO owner) apron at your discretion". Note the deliberate avoidance of the term "take-off". Similarly for landings, "winds 240@5, land at your discretion." Don't get involved in attempting to control an apron.

Lastly, an airport has grounds that are mowed near runways and between taxiways where many helicopters will want to practice certain movements as part of their training. Again, these are not technically part of the manoeuvring area, and landing and take-off clearances are generally not issued. We go back to the old, "depart at your discretion" and the same for landing.

Surface Movements

Ok, when a helicopter is getting ready for departure, they normally don't just start up on the runway (except in Flight Sim, of course). So if they plan to use a runway for departure (as they often must to comply with IFR departure procedures), they have to get to one first. There are a few different methods used by helicopters, and the methods often depend on what they have for landing gear.

For those with wheels, like Sea Kings, Blackhawks and so forth, the same taxiways and aprons are used for manoeuvring in the same way as fixed wing aircraft. The AIP RAC 4.6 tells us that pilots wishing to "ground taxi" should inform ATC of this desire when calling for taxi authorization.

If you're flying a Jet Ranger, Hughes 500 or other helicopter with skids or floats, ground taxiing can be difficult. Thus, there are two more modes of "surface" movements used by such choppers. One is called Hover Taxi, which is where the aircraft is flown at low altitude (within ground effect) and low airspeed, typically below 25 feet AGL and 20 kts, according to the AIP. The other is called Air Taxi, and is a little more free. The altitude is typically below 100 feet AGL, although speed and altitude chosen are solely the responsibility of the pilot. In this case, weather conditions must be considered as reduced visibility combined with the extra height can lead to disorientation. At the low altitude, disorientation could prove dangerous due to close ground proximity, and the reduced visibility gives rise to added danger of buildings and other aircraft near the intended path of the helicopter. Both the AIP and ATC MANOPS state that air taxi is the prefered method of operation for positioning a helicopter on the field, and, by default, clearances for helicopters to taxi will normally be issued with the term "air taxi" unless otherwise requested by the pilot.

ATC and Ground Movements

In either case mentioned above, controllers should be cautious of allowing helicopter operations near known groups of people or equipment, and especially around light aircraft. Anyone who has been near a helicopter at lift-off, touchdown, or air taxi can vouch for the high speed winds produced by the rotorwash. Light objects and debris, can be thrown around quite easily. Also, light aircraft are designed to ride the wind, and the winds produced can be quite strong. They have the potential for actually flipping a light aircraft over if he taxis nearby a helicopter in the hover, especially a heavier or dual rotor chopper. Considering this, ATC should attempt if at all possible to ensure helicopter operations on controlled airport surfaces are kept away from light aircraft and other vehicles and pedestrians, or the other way around. Also, for pilots, make sure you keep your distance from light aircraft that aren't tied down.

Another thing to consider is wake turbulence. For example, cross a medium weight category helicopter over a runway being used for circuits for light aircraft. Sound like a bad idea? Yup. The good news? You can't get the day off from an incident of this nature in our simulated environment. Wake turbulence is not a factor here.

As mentioned earlier, unless a pilot specifically requests ground taxi or hover taxi, issue clearances for taxiing using the term "air taxi". For example, "WOLF42 cleared air taxi Echo, across runway 24, Delta, across runway 29, Charlie to the apron."

ADDENDUM

In the previous topic Airport Operations Part 2: Taxiing, I stated that ATC MANOPS directs ground controllers to avoid use of the term "cleared" when issuing taxi instructions. Notice the phraseology examples in this topic. ATC is supposed to say "cleared air taxi ..." to a helicopter. Interesting contrast. I haven't found any concrete information to explain it, but the fact remains these two instructions are as they are in ATC MANOPS.




There you have it. The basics of helicopter operations are quite similar to fixed-wing operations, but there is increased flexibility. They are different, and so they have slightly different treatment in some cases, but for the most part, treat helos like anything else. As usual, if you feel I've left something out, or if you learned something, I'd be happy to hear from you at moxner@nbnet.nb.ca. Thanks for taking the time to read!