DUAS 0032 - NOTAMs and whether they get read

Initial Report

I completed an RPAS Notification form stating flight date, time and geo-location. I have completed these dozens of times for our quarry locations. This information was sent to [the Military Air Movements Cell (MAMC)] at SWK-MAMCLFCOORD@mod.gov.uk. On the email, I also add my phone number and the times it will be answered or leave a message. In addition, I also filled out a report of the drone flight on Altitude Angel.

I was flying the drone (a Sensefly eBee X – fixed wing), which is flown automatically by GNSS control through the calculated waypoints using eMotion 3.  I was about to conduct my second flight over the southern end of the quarry and was setup on the western tip, which provides a 360degree view for over one kilometre in any direction. When I fly, I always have my second phone open on Flight Radar. I had the laptop open, the drone powered and was designing the flight for upload when I heard an aeroplane to my west. I looked in that direction and saw a black, fast-moving low-level prop engine plane. I watched it and worked out it was approximately one kilometre to my west; I watched it travel south to north.

I looked at Flight Radar, clicked on the plane icon and then saw it was RAF Texan flying low and fast. As it reached the end of this leg it turned west (further away) from the quarry. I then noticed a second icon on the screen and waited for this one to fly past as it was on the same trajectory as the first one. I decided to wait and removed the battery from the drone. As the second RAF Texan completed the south to north trajectory it turned east and then south. It flew south directly over the quarry along its long north south axis. I watched it fly to my east by approximately 150-200m and approximately 25m above my head.

I am concerned that this happened because I had filled out the Military Notification of RPAS Activity. I have had several phone calls from pilots asking me to not fly when they are close or passing over the quarries after I have completed the form. I always consent to their request – the GVC course showed the aftereffects of a bird strike on a military helicopter.

After the flight I checked the RPAS Activity form was filled in correctly and had been sent, it was on both accounts.  Possible external factors to consider were: a) the information I sent was not entered into the RPAS Activity dataset; b) the information was entered but too late to affect the flight; or c) the data was entered but not acted upon by the pilot(s). I did not receive a message stating the information was in the system or a phone call from a pilot.

Recent addition from the reporter: just a note, since the overfly of the quarry by the RAF Texan aircraft, I have notified the Military of several flights I have since conducted at our other quarries. On each occasion I have had a confirmation reply that my notification of a drone flight has gone onto their system.

Lessons learned: Always use what is available – Flight Radar in this case; if something is close by – wait and only fly when the aircraft has moved away; never rely on forms, even though this is the primary source of information.

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RAF Safety Centre Comments

A civilian drone operator reported that they flew their fixed wing drone at a pre-planned location, a quarry in Devon. Ahead of conducting their second flight of the day, they report that they observed a “black fast moving low level propellor engine aeroplane” fly overhead their planned operating location at approximately 25m (~82ft) AGL, which concerned them as they had submitted a Military Notification of RPAS Activity the day prior to their intended flights. They believed the aircraft to be an RAF-operated Texan.

During investigation of this report, the following was concluded:

Military Notification of RPAS Activity. Interrogation of the military deconfliction tool shows that the drone operator did submit a notification to the Low Flying Booking Cell. This notification was displayed on the deconfliction tool.

  • Texan Ops. Contact with the Texan operating squadron confirms that they did have aircraft operating in this location at that time, conducting a pairs land away sortie [a 2 aircraft mission with a student flying one of the aircraft]. After discussion with the pilot of the aircraft believed to have overflown the drone operator’s location, they outlined their usual actions when an RPAS notification presents in the planning phase. Further interrogation of the deconfliction tool shows that the Texan pair’s planned low-level route would keep them laterally displaced from the RPAS notification.
  • Texan Height. Contact with the operating squadron confirmed that their routine MSD [Minimum Separation Distance from the ground] is 250ft, and that it is highly likely that the drone operator’s estimation of 25m (~82ft) AGL is incorrect. Dependant on the drone operator’s exact location, it is estimated the aircraft would have been at approximately 400-500ft.

Through discussion with members of the operating squadron, including the pilot of the aircraft believed to have overflown the drone operator’s location, they confirmed that the Military Notifications of RPAS Activity inputted to the deconfliction tool are factored into planning for Texan Ops. These notifications are routinely presented during the planning phase and crews will attempt to deconflict through time by contacting the drone operator in advance. If contact is not achieved, they will deconflict through lateral and/or vertical separation. If any off-route flying is conducted, which is often the case given the training demands of military aircraft, the notifications will be treated the same as a NOTAM and subsequent action taken to avoid laterally/vertically.

Further discussion with members of the operating squadron revealed that whilst the Military Notifications of RPAS Activity are greatly appreciated by crews as a barrier to prevent mid-air collision with a drone, they do come with certain limitations. This is due to the following commonly observed factors:

  • Drone operators will often not answer their listed contact numbers, despite numerous attempts to call by crews.
  • Drone operators’ intended operating locations often differ from those displayed on the deconfliction tool when contact with them is established.
  • Drone operators’ intended operating times often differ from those displayed on the deconfliction tool when contact with them is established.

After a review of the occurrence findings, we offer the following observations:

  • The current method of notification for drone operations is a useful barrier in the prevention of midair collision and we would strongly encourage drone operators to continue this good practice. The perceived weaknesses in the system, highlighted above, should be shared in order to educate and increase awareness which should improve the utility of this process for both aviators and drone operators. It is important to note that a notification like this will not warrant an avoid for our military crews but is extremely valuable in providing enhanced situational awareness.
  • Due to the fast-paced and involved nature of pre-flight briefing, it may not always be possible for the crew to contact the drone operator prior to flight. The system is not 100% effective and is certainly no guarantee that deconfliction will be achieved; for example, a crew may have already taken off when a late-notice drone flight is notified, or a take-off time is delayed which then brings a conflict that previously didn’t affect into play. Weather and other operational elements experienced inflight may also cause a military flight to deviate from their originally planned routing.
  • See and avoid remains the primary barrier to mid-air collision with a drone, but due to the small size of the majority of drones and the nature of the fast, low-level flying that the military conduct, the military pilots are reliant on drone operators enacting this mitigation barrier and landing their drone (or manoeuvring to a safe position) on seeing or hearing an approaching aircraft. This is in-line with the CAA published Drone and Model Aircraft Code – this code of conduct should continue to be highlighted to operators to ensure that they are following best practice and flying safely and legally.

We absolutely applaud the approach of the drone operator involved in this incident and their proactive actions to preserve air safety. Please continue to notify and report as this is the most effective way of increasing our situational awareness. I would again promote the promotion and use of the CAA Drone and Model Aircraft Code to ensure safe and legal operating. The military continues to educate our crews on this particular risk and, with more and more drones taking to the skies, we will continue to develop our procedures to ensure the best protection for our crews.

CHIRP Comment

There are some great learnings from both the reporter and the response from the RAF. We understand that the Texan aircraft had had to conduct a formation navigation turn in the area and these manoeuvres are demanding on students. As a result, it is therefore likely that student pilot may have become task focussed on the turn at the expense of the drone notification, albeit flying over the area at 4-500ft according to the RAF investigation.  Judging the height of aircraft above the ground is notoriously difficult to do and so, although we do not question the drone operator’s assessment, we cannot make any comment on what the actual height of the Texan was.  One thing to note however is that the altitude shown on FlightRadar24 will be based on transponder altitude of 1013hPa, and so will bear little resemblance to the actual aircraft altitude (unless of course the actual QNH happened to be 1013hPA) and corresponding height above the ground.

The topic of notification of drone flights and NOTAMs is currently a matter of some discussion. The one thing that is certain is it is important to read NOTAMs and other notification information when planning a flight, irrespective of whether the flight is crewed or uncrewed. On this occasion it was opportune that the drone wasn’t flying when the Texan flew over the quarry but, had it been flying, there is every chance that the drone pilot would have felt the obligation to land. This might then have resulted in them re-flying the whole site again to capture a complete data set.

There is a reliance on the drone pilot to avoid crewed aviation or, if it is necessary, to land. Although this is not specifically within SERA.3210 ‘Right-of-way’(c)(2) as one of the a priorities for converging aircraft, because the small size of a drone makes it much more difficult for a crewed aviation pilot to see it, best practice means it is incumbent on the drone pilot to move out of the way or preferably land should there be a potential for conflict. SERA.3205 ‘Proximity’ states that: “An aircraft shall not be operated in such proximity to other aircraft as to create a collision hazard”, which mandates the overarching requirement for all aviators to avoid collisions.

It is worth emphasising that just because a pilot has issued a NOTAM, it does not automatically give them a right of way or an assumption that their notified airspace will be avoided. H-series NOTAMs are warnings only, not restricted airspace (albeit it’s always sensible to avoid a NOTAM area whenever feasible). This applies both to crewed and uncrewed aircraft flight crew. Drone pilots will build confidence in the crewed-aviation community if they give accurate position and timing details of their flights in NOTAMS and aim to stick to them. Also, when completing a NOTAM, a pilot is well advised to enter their observer’s mobile number as the point of contact on the day, rather than an office telephone number. This enables other pilots to contact them directly to discuss how to best avoid potential airborne conflicts. Based on experience, CHIRP would recommend the pilot filing the NOTAM also verifies the correct point of contact, including the telephone number, in the subsequent NOTAM because ACOMS have been known to transpose telephone numbers incorrectly in the past.

For clarity, it is worth emphasising that approximately 90% of drone activity in unsegregated airspace does not involve drones flying from A to B, but rather drones performing data capture activities in a volume of airspace that is often delineated as a bubble and that tends not to be linear. It should be noted that when a Drone Operator or a Model aircraft site informs the military, via the Military Airspace Management Cell (MAMC), of planned activity, it does not automatically generate a NOTAM. It only generates a NOTAM if the activity is exceptional e.g. above 400ft etc. There are occasions when issuing a NOTAM for a Drone flight under 400ft would enhance safety. An application to do this in the past has resulted in a refusal by the NOTAM office and this may be worth reviewing.

Another suggestion made by the CHIRP Board is that it is important to check NOTAMS and the AIP, so that permanently notified sites that are listed in the AIP are picked up, as well as any sites that are temporarily listed in the AIP via the use of a NOTAM. The UK Airprox Board has separately recommended to the military that Model Flying sites for aircraft over 7.5kg should be marked on their VFR charts. The recommendation is currently being implemented in appropriate areas.

Finally, it should be noted that if a Drone Operator is flying in an FRZ, it is the responsibility of the Aerodrome that controls the FRZ to submit a NOTAM, not the Drone pilot.