Aviation Topic of the Week
By Michael Oxner,
November 23, 2003
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:
- Fixed wind aircraft are to fly the circuit at 1,200 feet
- Jet aircraft at 1,700 feet
- Helicopters at 700 feet.
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!