DEP ARTMENT OF THE AI R FORCE

HEADQUARTERS AIR FORCE FLIGHT STANDARDS AGENCY 

10 Jun 16

MEMORANDUM FOR HQ FAA/AGC-10

FROM: HQ AFFSA/XOF

 6500 South MacArthur Blvd, Bldg 4

 Oklahoma City, OK 73169

SUBJECT: 14 CFR Exemption 4371 Renewal (Regulatory Docket FAA-2000-8093)

1. FAA Exemption 4371 was granted to the United States Air Force on 21 Jun 85; as amended 

to 4371M on 19 April 2013, it exempts USAF aircraft from the provisions of Title 14, Code of 

Federal Regulations § 91.177(a)(2) and 91.179(b)(1). Military Training Route (MTR) operations 

are not governed by this exemption since their operations are covered in FAAO 7610.4. The 

requirement for USAF aircraft to conduct low-level operations without complying with en route 

minimum altitudes for flight under instrument flight rules (IFR) or direction of flight 

requirements for IFR en route segments in uncontrolled airspace has changed. 

2. At a minimum, the USAF requests that the FAA grant a renewal of the parameters within the 

current Exemption 4371M. The current exemption states:

a. “Operations under this exemption must be conducted at an altitude of at least 250 feet 

(with Terrain Following/Terrain Avoidance (TF/TA) Radar Systems) above the highest 

obstacle along the route of flight or 500 feet (without TF/TA) above the highest obstacle 

within 3 nautical miles (nm) of the course to be flown over mountainous and other areas. 

Rotary-Wing aircraft may operate at an altitude of at least 100 feet (with TF/TA) above 

the highest obstacle along the route of flight.”

b. “The maximum route length authorized under this exemption is 40NM.”

3. However, due to technological advances in aircraft systems, as well as current and future 

operational requirements, the Air Force needs to train aircrew and employ aircraft at altitudes 

lower and distances longer than granted in the current exemption Therefore, the USAF requests 

the following amendments to 4371M:

a. All aircraft operating within Special Use Airspace (SUA):

i. May fly as low as the bottom of the SUA floor when authorized by the 

appropriate military authority.

b. Fixed-Wing Aircraft operating IFR outside SUA or MTRs:

i. Minimum altitude when employing Terrain Following/Terrain Avoidance 

(TF/TA) procedures will be no lower than 200 feet Set Clearance Plane 

(SCP).

ii. Minimum altitude when employing visual low-level procedures will be no 

lower than 100 feet above obstacles.
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c. Rotary-Wing Aircraft operating IFR outside SUA or MTRs:

i. Minimum altitude when employing TF/TA procedures will be no lower than 

100 feet SCP.

ii. Minimum altitude when employing visual low-level procedures will be no 

lower than 50 feet above obstacles.

d. Tilt-Rotor Aircraft operating IFR outside SUA or MTRs:

i. Minimum altitude when employing TF/TA procedures in “Airplane” mode 

will be no lower than 100 feet SCP.

ii. Minimum altitude when employing TF/TA procedures in “Conversion” mode 

will be no lower than 50 feet SCP.

iii. Minimum altitude when employing visual low-level procedures in “Airplane” 

mode will be no lower than 100 feet above obstacles.

iv. Minimum altitude when employing visual low-level procedures in 

“Conversion” mode will be no lower than 50 feet above obstacles.

e. All aircraft operating IFR outside SUA or MTRs under this exemption are limited to a 

maximum route length of 240NM. 

4. The requested altitudes and route lengths represent an attempt to update the current exemption 

to complement newer capabilities of USAF aircraft and aircrews. Low-level flight is an 

operational requirement for USAF aircrews performing missions in the support and defense of

national interests and public safety. As a result, aircrews must be trained and proficient with the 

latest flight technologies and procedures in order to ensure a high probably of real-world mission 

success. The lower altitudes will allow aircrew to deploy aircraft resources closer to mission 

objectives within more austere terrain and weather conditions. The requested maximum route 

length of 240NM provides adequate terrain variation and approximately 60 minutes of flight 

time (whereas a 40NM route only provides 10 minutes). This additional time is necessary to 

replicate effective mission scenarios and provide proper training credit as mandated by USAF 

regulations. It will also reduce the negative impacts to safety and fuel efficiency that would be 

created by multiple route and altitude changes.

5. Safety will be ensured during all of the above military operations through a combination of 

airframe technology, training, and mission planning. The proper military authority will limit 

operations by airframe based upon capabilities (i.e. TF/TA set performance, operating low-level 

airspeeds, etc.) and mission requirements. A large number of military airframes must train to 

low-level operations to accomplish their mission-set and it is therefore imperative for them to 

perform low-level IFR operations below 1000 feet.

a. USAF aircraft possess the following technologies that give them the capability to fly

safely at the requested altitudes and route lengths.

i. Fixed-wing aircraft possessing the TF/TA radar are capable of flying at lower 

altitudes of 200’ SCP in IMC conditions. When employing visual low-level 

procedures, fixed-wing aircraft possessing the Operational Flight Programs (OFP) 

have the capability to alert aircrews through visual and audio cues if they descend 
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below the minimum altitude and provide a climb command that is displayed on 

the Primary Flight Reference instrumentation. In conjunction with the TF/TA 

radar and OFPs, aircrews utilize Night Vision Devices (NVDs), Infrared 

Detection Set (IDS), Electro-Optical Infrared (EO-IR), Traffic Alert and Collision 

Avoidance System (TCAS), and Ground Collision Avoidance System (GCAS) to 

assist in safely avoiding terrain, obstacles, and other aircraft. 

ii. Rotary-wing aircraft possess a dual radar altimeter for low-level flight which 

includes an audible and visual altitude alert feature with an additional radar 

altitude display on the heads down display (HUD), as well as a Forward Looking 

Infrared Radar (FLIR) for augmenting day and night vision. 

iii. Rotary-wing aircraft possessing the Helicopter Terrain Awareness and 

Warning System/Traffic and Collision Alert Device (HTAWS/TCAD) have the 

capability to provide audio and visual warning of terrain, obstacles, and other

transponder equipped aircraft. The Electronic Horizontal Situation Indicator 

(EHSI) combines course and heading guidance, weather data, as well as map and 

airspace overlays on a single customizable display reducing pilot work load and 

improving situational awareness. NVD modifications enhance visual acuity by 

significantly reducing non-compatible emissions from within the cockpit while 

ensuring instrumentation is easily readable.

iv. Tilt-rotor aircraft possessing the TF/TA radar are capable of flying at lower 

altitudes of 100’ SCP (“airplane mode”) and 50’ SCP (“conversion” mode) in 

IMC conditions. Additionally, this radar is used in conjunction with NVD and 

FLIR technology in order to ensure safe operations. 

v. Finally, USAF aircraft possess embedded GPS and RNAV navigation systems 

to increase lateral positional accuracy and awareness.

b. The USAF believes it can conduct low-level operations at the same level of safety, in 

class G airspace, outside of Military Training Routes and Special Use Airspace without 

endangerment to the public.

i. Flights within class G airspace will be limited to the minimum needed to 

accomplish mission and training objectives. USAF aircraft will continue to 

attempt to conduct low-level flights within SUA and MTRs to the maximum 

extent possible. 

ii. Flight duration at the lower altitudes will be limited to the minimum needed to 

accomplish mission and training objectives.

iii. TF/TA equipment have been tested and proven to be effective and safe at the 

requested altitudes and within the capabilities of the aircraft. Aircrews are 

augmented with the numerous technologies listed in the previous paragraph to 

assist in safely avoiding other aircraft, obstacles, and persons. 
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iv. Aircrews receive extensive training on the employment of low-level 

equipment and procedures utilizing simulators, day VFR training flights, and 

night VFR training flights before performing any IMC low-level operations. This 

is further complemented with continuous training sorties which are designed to 

build aircrew proficiency in both day and night low-level missions. 

v. The USAF routinely uses risk-mitigation techniques such as defined climb 

points, thorough route-study, avoidance of populated areas, and review of 

emergency actions. Training is conducted in sparsely populated areas, overwater, 

or within Low Altitude Tactical Navigation (LATN) training areas. 

vi. Where feasible, pilots are augmented with additional crewmembers who 

monitor systems and altitudes and detect possible risks with terrain, other aircraft, 

and overall public safety, especially when employing visual low-level procedures. 

vii. Current navigation systems utilizing GPS and RNAV technologies will 

provide the same positional accuracy and awareness and have no negative effect 

upon extending route lengths to the requested 240NM.

 

c. Granting this amendment is in the public interest because it provides USAF aircrews 

the ability to train with the newest capabilities which will further increase the probability 

of success in performing missions that support national security, search-and-rescue, 

humanitarian assistance, and disaster relief, even in austere conditions. Additionally, 

such training will ensure aircrews remain qualified and proficient to perform at these 

lower altitudes without posing a threat to public safety.

6. If this exemption is not granted, the USAF will not be able to train to meet current real-world 

flight operational requirements at the lower altitude parameters. USAF flying operations must 

continuously adapt to an ever changing mission set to meet national security, search-and-rescue, 

and humanitarian relief mission needs. Realistic and adequate training scenarios may be 

hindered or not available with SUA or MTRs. Additionally, without approval, all training for 

IFR low-level operations will be forced to occur in MTRs, increasing MTR workload as well as 

increasing chances of flight-path deconfliction challenges. Safety could be negatively impacted 

and critical training for contingency operations will be lost impacting the USAF’s ability to 

accomplish dynamic domestic and global missions.

7. Please contact me at (405) 734-4298 or hqaffsa.xof@us.af.mil if there are any questions or

concerns. Thank you in advance for your assistance.

6/10/2016

X Christopher M. Shea

CHRISTOPHER M. SHEA, Lt Col, USAF

HQ AFFSA, Flight Directives Division

Signed by: SHEA.CHRISTOPHER.M.1010528379