1. Rotorcraft Unique Considerations
AEA
January 31, 2012

2. OUTLINE Rotorcraft Unique Considerations
Airplane versus Helicopter comparison

3. Unique Rotorcraft Considerations
Category Airplane Helicopter Concerns
VFR minimums sm day Clear of clouds
91.155(b) sm night EADI/PFD, TAWS
Special VFR sm flight vis No visibility specified
91.157(b) daylight No time specified
Takeoff Grd Vis 1sm No visibility specified
91.157(c)
Basic VFR weather minimums
91.151b
(1) Helicopter. A helicopter may be operated clear of clouds if operated at a speed that allows the pilot adequate opportunity to see any air traffic or obstruction in time to avoid a collision. [(2) Airplane, powered parachute, or weight-shift-control aircraft.. If the visibility is less than 3 statute miles but not less than 1 statute mile during night hours and you are operating in an airport traffic pattern within one-half mile of the runway, you may operate an airplane, powered parachute, or weight-shift-control aircraft clear of clouds.]
(b) Special VFR operations may only be conducted--
(1) With an ATC clearance;
(2) Clear of clouds;
(3) Except for helicopters, when flight visibility is at least 1 statute mile; and
(4) Except for helicopters, between sunrise and sunset (or in Alaska, when the sun is 6 degrees or more below the horizon) unless–
(c) No person may take off or land an aircraft (other than a helicopter) under special VFR--
(1) Unless ground visibility is at least 1 statute mile; or

4. Unique Rotorcraft Considerations
Category Airplane Helicopter Concerns
Stability Inherently Stable Limited Stability EADI / PFD
Trim Aerodynamic None – unless: SAS / AP
Temperature Airflow in flight Greenhouse effect Equip Qualification
Vibration Propeller Main/Tail rotor Equip Qualification
Stability – A trimmed aircraft has positive stability
A helicopter has neutral of negative stability
This places emphasis on misleading Attitude indications.
Difficult to fly in low visibility with no discernable horizon
Trim - Airplanes have aerodynamic forces to provide force gradient
Helicopters have no force gradient with irreversible hyd systems
Temp - Temperature: The green house effect on the temperature requirements for equipment, due to the amount of large glass windows typically found in rotorcraft. Some equipment may not be qualified to operate at these extreme hot temperatures.
Vibration – Props are usually the main vibraiton source and are high frequency
- Main rotor is broken down into 1 omega and N omega
- Vertical and lateral components

5. Unique Rotorcraft Considerations
Category Airplane Helicopter Concerns
HIRF Dist from Xmit Fly close to XMIT Equip Qual
System Separation Adequate Limited Wire Bundle runs
Antenna Ground Plane
Relative to fixed-wing GA aircraft, Rotorcraft capabilities: allow it to be used in a wide variety of operations that expose it and its occupants to a wider variety of hazards than fixed wing aircraft (i.e. Hospital Emergency Medical Services (HEMS), Logging, Air crane, Police DEA, Agriculture, sight seeing very close to obstacles, terrain and urban environments).
closer to ground based antennas they are more susceptible to a higher HIRF environment
Takeoff – Generally the nose is raised to liftoff,
Helicopters nose down to accelerate. This may be an issue for some AHRS

6. Unique Rotorcraft Considerations
Category Airplane Helicopter Concerns
Takeoff Attitude Nose Up Nose Down AHRS
Rate of turn Typically 6°/s up to 60°/s AHRS
The helicopter flight control control rods take up a lot of space beneath the cabin.
System separation: is more challenging due to fewer places to mount, route wires, and install components compared to fixed wing aircraft. There is typically no extra room in the “cabin” or nose area to install any equipment, therefore pretty much everything is to be considered as mounted in the cockpit area.
Battery location
limited space for antennas and to ensure adequate ground plane
Limited space for wire runs

7. Unique Rotorcraft Considerations
Category Airplane Helicopter Concerns
FHA Classification Class No class distinction Equipment
Class 2
Class 3
Class 4
Class 1 - Typically SRE 6,000 pounds (lbs.) or less
Class 2 - Typically MRE, MTE and STE, 6,000 pounds or less
Class 3 - Typically SRE, STE, MRE, and MTE greater than 6,000 Lb
Class 4 – Communter Category