14 CFR Part 27 - Airworthiness Standards: Normal Category Rotorcraft

14 CFR Part 27/FAR Part 27

This part prescribes airworthiness standards for the issue of type certificates, and changes to those certificates, for normal category rotorcraft with maximum weights of 7,000 pounds or less and nine or less passenger seats.

Airworthiness Standards: Normal Category Rotorcraft

It is the title of 14 CFR Part 27.

Category A

According to 14 CFR Part 27, provided the requirements referenced in appendix C of this part are met, multiengine rotorcraft may be type certified as

September 16, 1992

Each applicant must show that each occupant's seat is equipped with a safety belt and shoulder harness that meets the requirements of 14 CFR Part 27 for each rotorcraft manufactured after

single-point release

Each occupant's seat must have a combined safety belt and shoulder harness with a

rotorcraft type certification basis

The safety belt and shoulder harness must meet the static and dynamic strength requirements, if applicable, specified by the

October 18, 1999

For rotorcraft with a certification basis established prior to October 18, 1999, the maximum passenger seat capacity may be increased to eight or nine provided the applicant shows compliance with all the airworthiness requirements of this part in effect on

6,000 pounds

Provided the number of passenger seats is not increased above the maximum number certificated and the applicant shows compliance with all of the airworthiness requirements of this part in effect on October 18, 1999, the maximum weight may be increased to greater than _______________.

safety belt plus a shoulder harness

To prevent the head of each occupant from contacting any injurious object, it must be protected from serious head injury by a _____________.

minimum weight

It must be established so that it is not more than the sum of the empty weight determined under 14 CFR Part 27.29.

maximum weight

It must be established so that it is not more than the highest weight selected by the applicant or the design maximum weight.

design maximum weight

It is the highest weight at which compliance with each applicable structural loading condition of this part is shown.

maximum weight

It is the highest weight at which compliance with each applicable requirement of this part is shown.

minimum weight

It is the lowest weight at which compliance with each applicable requirement of this part is shown.

design minimum weight

It is the lowest weight at which compliance with each applicable structural loading condition of this part is shown.

170 pounds

The minimum weight must be established so that it is not more than the sum of the weight of the minimum crew necessary to operate the rotorcraft, assuming for each crew member a weight no more than

170 pounds

The maximum weight must be established so that it is not less than the sum of for each seat, an occupant weight of _________.

14 CFR Part 27.29/FAR Part 27.29

The maximum weight must be established so that it is not less than the sum of the weight of usable fuel appropriate to the intended operation with full payload, the weight of full oil capacity, and the empty weight determined under ___________.

human external cargo

A total weight for the rotorcraft with a jettisonable external load attached that is greater than the maximum weight established under paragraph (a) of this section may be established for any rotorcraft-load combination if the rotorcraft-load combination does not include ___________________.

limit loads

The maximum loads to be expected in service.

ultimate loads

Limit loads multiplied by prescribed factors of safety.

limit loads

Strength requirements are specified in terms of limit loads and ultimate loads. Unless otherwise provided, prescribed loads are _____________.

1.5

According to 14 CFR Part 27.303, it is the amount of factor of safety that must be used.

3 seconds

The structure must be able to support ultimate loads without failure. This must be shown by applying ultimate loads to the structure in a static test for at least

longitudinal

The flight load factor must be assumed to act normal to the ________ axis of the rotorcraft.

center of gravity

The flight load factor must be assumed to be equal in magnitude and opposite in direction to the rotorcraft inertia load factor at the

Rotorcraft Flight Manual

Compliance with the flight load requirements of Subpart C must be shown with any practical distribution of disposable load within the operating limitations in the

3.5 and -1.0

The rotorcraft must be designed for a limit maneuvering load factor ranging from a positive limit of ____ to a negative limit of ____.

2.0 and -0.5

The rotorcraft must be designed for any positive limit maneuvering load factor not less than ____ and any negative limit maneuvering load factor of not less than ____.

rotor tip speed ratio

It is the ratio of the rotorcraft flight velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades.

30 feet per second

The rotorcraft must be designed to withstand, at each critical airspeed including hovering, the loads resulting from a vertical gust of

1.25

For turbine engines, the limit torque may not be less than the highest of the mean torque for maximum continuous power multiplied by

1.33

For reciprocating engines with five or more cylinders, the limit torque may not be less than the mean torque for maximum continuous power multiplied by

3

For reciprocating engines, the limit torque may not be less than the mean torque for maximum continuous power multiplied by 2, ______, and 4, for engines with four, three, and two cylinders, respectively.

0.75

Each dual primary flight control system must be designed to withstand the loads that result when pilot forces of _____ times those obtained under 14 CFR Part 27.395 are applied in opposition and in the same direction.

both

To meet the design criteria of paragraph (a) of this section, in the absence of more rational data, both of the following must be met:

1. One hundred percent of the maximum loading from the symmetrical flight conditions acts on the surface on one side of the plane of symmetry, and no loading acts on the other side.

2. Fifty percent of the maximum loading from the symmetrical flight conditions acts on the surface on each side of the plane of symmetry but in opposite directions.

Which of the statement is correct?

maximum weight

For specified landing conditions, a design maximum weight must be used that is not less than the

design maximum weight

A rotor lift may be assumed to act through the center of gravity throughout the landing impact. This lift may not exceed two-thirds of the

static and critical

Unless otherwise prescribed, for each specified landing condition, the tires must be assumed to be in their _________ position and the shock absorbers to be in their most _________ position.

maximum nose-up

The rotorcraft is assumed to be in the _____________ attitude allowing ground clearance by each part of the rotorcraft.

perpendicular

During maximum nose-up attitude, ground loads are assumed to act __________ to the ground.

1.33

Under braked roll conditions with the shock absorbers in their static positions, the limit vertical load must be based on a load factor of at least ______ for the attitude specified in 14 CFR Part 27.479(a)(1).

1.0

Under braked roll conditions with the shock absorbers in their static positions, the limit vertical load must be based on a load factor of at least ______ for the attitude specified in 14 CFR Part 27.479(a)(2).

0.8

The structure must be designed to withstand at the ground contact point of each wheel with brakes, a drag load at least the lesser of the vertical load multiplied by a coefficient of friction of ______.

external loads

The limit ground loads obtained in the landing conditions in 14 CFR Part 27 must be considered to be ___________ that would occur in the rotorcraft structure if it were acting as a rigid body.

critical

The __________ centers of gravity within the range for which certification is requested must be selected so that the maximum design loads are obtained in each landing gear element.

two-thirds

For specified landing conditions, a design maximum weight must be used that is not less than the maximum weight. A rotor lift may be assumed to act through the center of gravity throughout the landing impact. This lift may not exceed _________ of the design maximum weight.

autorotation

The main rotor structure must be designed to withstand critical flight loads and limit loads occurring under normal conditions of ________.

0.031

A change in downward velocity of not less than 30 feet per second when the seat or other seating device is oriented in its nominal position with respect to the rotorcraft's reference system, the rotorcraft's longitudinal axis is canted upward 60° with respect to the impact velocity vector, and the rotorcraft's lateral axis is perpendicular to a vertical plane containing the impact velocity vector and the rotorcraft's longitudinal axis. Peak floor deceleration must occur in not more than _______ seconds after impact and must reach a minimum of 30g's.

0.071

A change in forward velocity of not less than 42 feet per second when the seat or other seating device is oriented in its nominal position with respect to the rotorcraft's reference system, the rotorcraft's longitudinal axis is yawed 10° either right or left of the impact velocity vector, the rotorcraft's lateral axis is contained in a horizontal plane containing the impact velocity vector, and the rotorcraft's vertical axis is perpendicular to a horizontal plane containing the impact velocity vector. Peak floor deceleration must occur in not more than _______ seconds after impact and must reach a minimum of 18.4g's.

10 degrees

Where floor rails or floor or sidewall attachment devices are used to attach the seating devices to the airframe structure for the conditions of this section, the rails or devices must be misaligned with respect to each other by at least _____ vertically and by at least a _____ lateral roll, with the directions optional, to account for possible floor warp.

1,750 pounds

Loads in individual upper torso harness straps must not exceed _________.

2,000 pounds

Loads in individual upper torso harness straps must not exceed 1,750 pounds. If dual straps are used for retaining the upper torso, the total harness strap loads must not exceed _________.

1,500 pounds

The maximum compressive load measured between the pelvis and the lumbar column of the ATD must not exceed _________.

30 knots

A maximum forward velocity of less than _________ may be used in design if it can be demonstrated that the forward velocity selected would not be exceeded in a normal one-engine-out touchdown.

20 knots

For each float deployed after initial water contact, it must be designed for combined vertical and drag loads using a relative limit speed of ________ between the rotorcraft and the water.

catastrophic failure

It is an event that could prevent continued safe flight and landing.

Principal Structural Elements; PSEs

These are structural elements that contribute significantly to the carrying of flight or ground loads, the failure of which could result in catastrophic failure of the rotorcraft.

Threat Assessment

It is an assessment that specifies the locations, types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws, and impact or other accidental damage that may occur during manufacture or operation.

tests

The suitability of each questionable design detail and part must be established by ________.

critical part

It is a part, the failure of which could have a catastrophic effect upon the rotorcraft, and for which critical characteristics have been identified which must be controlled to ensure the required level of integrity.

critical parts list

It shall be established if the type design includes critical parts.

two separate locking devices

Each removable bolt, screw, nut, pin, or other fastener whose loss could jeopardize the safe operation of the rotorcraft must incorporate _____________.

nonfriction locking device

No self-locking nut may be used on any bolt subject to rotation in operation unless a _____________ is used in addition to the self-locking device.

weathering, corrosion, and abrasion

Each part of the structure must be suitably protected against deterioration or loss of strength in service due to any cause, including ______________, ______________, and ______________.

MIL-HDBK-5; MIL-HDBK-7; MIL-HDBK-23; ANC-18

Design values may be those contained in the following publications (available from the Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, Pennsylvania 19120) or other values approved by the Administrator. These are:

Metallic Materials and Elements for Flight Vehicle Structure

Title for MIL-HDBK-5

Plastics for Flight Vehicles

Title for MIL-HDBK-7

Composite Construction for Flight Vehicles

Title for MIL-HDBK-23

Design of Wood Aircraft Structures

Title for ANC-18

1.25

For each casting whose failure would preclude continued safe flight and landing of the rotorcraft or result in serious injury to any occupant, each critical casting must have a casting factor of not less than ____.

1.15

For each fitting whose strength is not proven by limit and ultimate load tests in which actual stress conditions are simulated in the fitting and surrounding structures, a fitting factor of at least ____ must be applied to each part of the fitting, the means of attachment, and the bearing on the joined members.

flutter

Each aerodynamic surface of the rotorcraft must be free from _______ under each appropriate speed and power condition.

primary flight controls

Controls used by the pilot for immediate control of pitch, roll, yaw, and vertical motion of the rotorcraft.

three thirty-seconds

No cable smaller than __________ of an inch diameter may be used in any primary control system.

MIL-HDBK-5 Volume 1 and 2

Pulley kinds and sizes must correspond to the cables with which they are used. The pulley cable combinations and strength values which must be used are specified in ________________.

3 degrees

No fairlead may cause a change in cable direction of more than ______.

autorotation

Each main rotor blade pitch control mechanism must allow rapid entry into __________________ after power failure.

50 percent

For main floats, the buoyancy necessary to support the maximum weight of the rotorcraft in fresh water must be exceeded by _____ percent for single floats.

60 percent

For main floats, the buoyancy necessary to support the maximum weight of the rotorcraft in fresh water must be exceeded by _____ percent for multiple floats.

maximum pressure differential

Each bag float must be designed to withstand the ______________________ that might be developed at the maximum altitude for which certification with that float is requested.

5'2" to 6'0''

Cockpit controls must be located and arranged with respect to the pilots' seats so that there is full and unrestricted movement of each control without interference from the cockpit structure or the pilot's clothing when pilots from ____ to ____ in height are seated.

1

Each closed cabin must have at least ____ adequate and easily accessible external door(s).

TSO-C114

A shoulder harness (upper torso restraint), in combination with the safety belt, constitutes a torso restraint system as described in ___________.

40 percent

When the safety belt and shoulder harness are combined, the rated strength of the safety belt and shoulder harness may not be less than that corresponding to the inertial forces specified in 14 CFR Part 27.561(b), considering the occupant weight of at least 170 pounds, considering the dimensional characteristics of the restraint system installation, and using a distribution of at least a 60 percent load to the safety belt and at least a _____ percent load to the shoulder harness.

13 pounds

When a headrest is used, the headrest and its supporting structure must be designed to resist the inertia forces specified in 14 CFR Part 27.561, with a 1.33 fitting factor and a head weight of at least ____ pounds.

1

There must be at least _____ emergency exit(s) on each side of the cabin readily accessible to each passenger.

19x26 inch

Each emergency exit prescribed by paragraph (a) of this section must consist of a movable window or panel, or additional external door, providing an unobstructed opening that will admit a _____-inch ellipse.

20,000 parts

The concentration of carbon monoxide may not exceed one part in __________ parts of air during forward flight or hovering in still air. If the concentration exceeds this value under other conditions, there must be suitable operating restrictions.

fireproof

Each ventilating air duct passing through any heater region and each combustion air duct must be ____________ for a distance great enough to prevent damage.

5 minutes

Each part of the structure, controls, rotor mechanism, and other parts essential to a controlled landing that would be affected by powerplant fires must be fireproof or protected so they can perform their essential functions for at least ___ minutes under any foreseeable powerplant fire conditions.

2.5

It must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static load equal to _____, or some lower load factor approved under 14 CFR Part 27.337 through 27.341, multiplied by the maximum external load for which authorization is requested.

3.5

It must be shown by analysis, test, or both that the rotorcraft external load attaching means and corresponding personnel carrying device system for rotorcraft-load combinations to be used for human external cargo applications can withstand a limit static load equal to ____ or some lower load factor, not less than 2.5, approved under 14 CFR Part 27.337 through 27.341, multiplied by the maximum external load for which authorization is requested.

type certificate

Each engine must have an approved ____________.

1.5

If an engine or rotor drive system cooling fan is installed, there must be a means to protect the rotorcraft and allow a safe landing if a fan blade fails. This must be shown by showing that each fan blade can withstand an ultimate load of ____ times the centrifugal force resulting from operations.