Helipad Construction

Basic Helicopter Pad Construction
for Line Crews
Revision 2011-1 March 28, 2011 BAC PO
Helipad Construction
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Basic Requirements ........................................................................................................ 1
Location ....................................................................................................................... 1
Slope of Side Hill ...................................................................................................... 1
Access ..................................................................................................................... 2
Overhead Hazards ................................................................................................... 2
Clearing Size ............................................................................................................ 2
Survivability .............................................................................................................. 2
Prevailing Winds ...................................................................................................... 3
Load Bearing Capacity ................................................................................................ 3
Shock Loading ......................................................................................................... 3
Configuration ............................................................................................................... 4
Hughes 500 Pad Configuration ................................................................................ 4
Astar Pad Configuration ........................................................................................... 6
Harmonic Vibration .................................................................................................. 7
Other Considerations ...................................................................................................... 7
Improperly Constructed Pads ...................................................................................... 8
Properly Constructed Pads .......................................................................................... 9
Conclusion .................................................................................................................... 11
Revision 2011-1 March 28, 2011 BAC PO
Summary
Every year support helicopters working for bush operations perform several thousand
landings and take-offs. A great number of these landings and take-offs are from
helipads constructed by line crews. These helipads serve as the main platform for
transporting crews to and from the work sites. It is essential for everyone’s safety that
these pads are constructed properly.
No excuse would be acceptable should there be an accident or mishap as a result of a
poorly constructed helipad.
Revision 2011-1 March 28, 2011 BAC PO
Helipad Construction
Properly constructed helipads are essential where access to work sites by helicopter is
required. In order to insure safe pads are constructed every time, a standard procedure
for pad construction must be followed. The procedure outlined here for pad
construction has been established to assist fallers in creating safe helipads.
By following this standardized method of construction it is possible to make pads that
are consistent in their load bearing capacity and have a familiar visual configuration for
the pilots. This uniformity in construction eliminates many potential dangers and gives
assurance to pilots that they have safe shut-down pads to land on.
The importance of safe, sound, and sturdy helipads can not be over stated. Nothing
should be taken for granted in the construction of helipads. The lives of everyone
working in helicopter logging, engineering, and silviculture are dependent upon how
thoughtfully and carefully these pads are put together.
Basic Requirements
The three basic requirements are proper location of the helipad, sufficient load bearing
capacity and configuration.
Location
There are a number of issues to think about when determining where to build a pad.
The following list summarizes some of the items to consider when determining where to
build a pad:
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Slope
Access
Building materials
Overhead hazards
Clearing size
Survivability
Prevailing winds
Slope of Side Hill
Pads can be built on steep ground if they are planned properly. The essential
requirement is sufficient rotor clearance for the helicopter. Do not build pads against
rock walls. Do not box the pilot into small confined spaces where he has no room to
maneuver or has restricted access to the pad.
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Always build level pads. Do not build pads that slope backward or to one side.
Access
It is preferable for the helicopter to be able to access the helipad from the back and both
sides. This gives the pilot the ability to deal with changing wind conditions as they arise.
Do not build pads in hollows. Build pads where the ground drops away, this gives a
good safety margin for rotor clearance.
Building Materials
Before building a pad have the following five things available:
 sound, stable, good sized stumps for the rear of the pad
 enough material in the immediate vicinity from which you can rip stringers and
cross members of sufficient soundness to support 1½ times the fully loaded
weight of the helicopter
 line level
 10” helical spikes
 high visibility paint
Overhead Hazards
All overhead hazards in the immediate and near vicinity of the pad must be removed.
This includes all danger trees that could fall and strike the pad, any overhead hazard
such as limbs, widow makers, or loose bark. In addition consider any material hanging
off rock bluffs uphill from the pad as potential dangers and remove them if possible.
Clearing Size
On initial construction of the helipad make sure the pilot has enough clearance around
the pad to do a 360° turn if necessary. It is difficult to vertical in and out of a tightly
confined space and every opportunity must be given to the pilot to deal with changing
wind patterns.
Survivability
In determining where to construct helipads choose a spot where they will not be
destroyed by timber that still has to be felled. There is no point in building a pad in a
location where timber uphill will destroy the pad.
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Prevailing Winds
Very often there are settings where a prevailing wind exists. Take this wind into
consideration when you are determining the orientation of the pad on the side hill. If
there is sufficient room the pad can be oriented in any direction.
Load Bearing Capacity
It is necessary to build a pad of sufficient strength and capacity to withstand two
conditions:
 the shock loading effect on the pad if an emergency shut down is necessary
 the harmonic vibrations set up in the pad while the helicopter is sitting
Shock Loading
The type and size of material used to build the pad is critical. The timbers used for
construction have to be able to withstand the forces generated by a fully loaded
helicopter. The forces produced will be directly related to the loaded weight of the
helicopter. Thus a pad constructed for use by an Astar or Long Ranger will have to be
heavier than a pad constructed for a Hughes 500.
Always make sure any helipad you construct is heavy and sound enough to allow the
pilot to shut down the helicopter on the pad in an emergency.
The following table is a guideline which can be used when determining the size of the
stringers and cross members required to support the weight of an Astar weighing 5000
pounds.
Timber Pads
Rough Lumber
Length
(ft)
Cedar
Cedar
(inches)
Cross
Members
12
8
6x6
Stringers or
Substringers
12
13
14
16
10
11
12
13
8x8
8x8
8x8
8x8
When picking out material to use in construction, make sure there are no defects in the
wood such as splits, cracks, rot, or bunch knots.
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Configuration
There are two basic configurations which can be used when constructing a pad. One is
suitable for the Hughes 500 and the other for an Astar or Long Ranger. If the Hughes
500 pad is built to withstand the weight of an Astar it can be the primary type of pad
built.
However, keep in mind that if a medivac from the side hill is necessary and a staging
area is required, a large pad allowing easy access to the helicopter has distinct
advantages.
Hughes 500 Pad Configuration
Some items to consider when building the pad are:
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the distance between stumps
the span of the stringers
the length and width of the pad
the height of the pad above ground
Distance between Stumps
The optimal distance between stumps is 10 to 12 feet. However, if no appropriate
stumps can be found, the difficulty can be overcome by building the pad on a heavy
cross member which spans the two rear stumps.
By using this technique you can have stumps greater than 12 feet apart and still build
the same configuration as above. The critical factors are the diameter of the stringers
and cross members with which the helipad will be constructed.
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It is not necessary to have four stumps for pad construction. But it is essential to have
two solid and stable stumps which support the back of the pad. The front can be
supported either by the ground or rounds of wood cut the correct height.
Span of Stringers
The greater the distance the stringers have to span, the heavier they have to be (refer
to the table above). If the stringers span too great a distance they must be blocked mid
way to add rigidity to the structure and to prevent excessive movement.
Cross Members
The cross members should either be round logs of uniform size, or ripped boards of
sufficient width and thickness to safely support the total weight of the helicopter.
Do not make the cross members too short, too narrow or too thin. The minimum
dimensions for cross members on the Hughes 500 pad should be 12’L x 6”W x 6”T. A
more desirable length for the cross member would be 14 feet.
Make sure all cross members are the same height; especially the cross member in the
middle. If they are not even and level the helicopter can be high centered, making it
unstable on the pad.
Remember, this is the platform you will be using to get in and out of the helicopter.
Make it wide enough so you have easy access to and from the helicopter.
Height above Ground
Build the pads high enough off the ground so there is sufficient tail rotor clearance. Also
ensure there is adequate main rotor clearance in front of the helicopter.
Do not build helipads any higher than necessary for safe clearance of the tail and main
rotor. Excessively high pads are difficult to access and pose a danger if someone
should fall from the pad. Do not build pads higher than 6 feet off the ground.
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Astar Pad Configuration
The skid configuration for an Astar or Long Ranger is different from that of the Hughes
500. The pad for these helicopters requires more stringers. It is essentially a 12’ x 12’
square with six to eight cross members.
The Astar and Long Ranger are heavier helicopters and require sturdy stringers and
cross members. Both machines are longer and need a clearing of 75’ in diameter.
Remember, the Hughes 500 pad if constructed properly and with heavy enough timbers
will support an Astar or Long Ranger. One thing you want to keep in mind when using
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the 500 pad for a Jet Ranger, Long Ranger or Astar is the necessity of accessing the
rear storage compartment on these helicopters.
In order to accommodate for this requirement, make sure you build an extension onto
the back of the pad which allows you access to the storage compartment of these
helicopters.
Harmonic Vibration
The other destructive force that helipads have to withstand is vibration. A helicopter
sitting on a pad with power on transfers a vibration to that pad. If the vibration is
allowed to build it is capable of collapsing the pad. This is especially true with heavy
helicopters like the Astar and Long Ranger.
In order to counter act this force it is crucial to build pads that are rigid and do not allow
excess movement in the pad.
When necessary cross brace the pad to prevent the tendency of it to oscillate and
possibly collapse.
Other Considerations
The preceding guidelines do not cover all aspects of helipad construction. They are the
basics for constructing safe and stable helipads capable of standing up under constant
use.
The following list itemizes some things that should not be done:
 do not shim pads
 do not construct helipads on bucked logs or windfalls
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Improperly Constructed Pads
You can see the safety concerns with
shimming pads. Especially when you
consider the dangers associated with
excessive vibration.
Do not put shims under the back of
the pad to level it. If necessary cut
the stump again to level the pad
rather than inserting a shim. Use a
line level and get the stumps the
correct height initially.
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Do not build pads like the one below. This pad would be incapable of supporting a fully
loaded helicopter in the event of an emergency shut down.
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Properly Constructed Pads
The following two photos are examples of pads which are adequately built and will meet
all the requirements we have itemized.
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Conclusion
The most important consideration when constructing a helipad is safety. It is absolutely
essential to construct sound, level, and firm pads. These pads must be able to support
the weight of a fully loaded helicopter. The pads must be placed in a position that does
not compromise or hinder the pilot. All hazards surrounding the pad must be removed.
All pads are required to be shut-down pads. Besides supporting the weight of the
helicopter these pads have to be able to withstand the vibration associated with the
running helicopter or the vibrations the helicopter would generate if it had to start up on
the pad.
Keep in mind at all times, the helipads which you are constructing are your life line. Do
not compromise your life or anyone else’s. Do not cut corners. Do not perform shoddy
workmanship. Do not use substandard building materials.
When the pads are constructed initially the following basic guidelines are to be kept in
mind.
1. Any material used in the construction of the pad must be capable of supporting a
minimum weight of 4,500 pounds.
2. All openings are to be large enough that they allow the pilot to do a full 360º turn
in the opening.
3. There is to be no branches overhanging the opening into which the helicopter is
descending.
4. There is to be no danger trees within 2 ½ tree lengths of the pad. None what so
ever. No exceptions.
5. The approach to the pad must be clear of any obstructions.
6. There must be no debris around the pad which could interfere with the rotors.
7. All pads must be constructed with a line level.
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