The UK Civil Aviation Authority (CAA) has updated regulations for air-ground radio operators following an incident at a UK airfield when two aircraft collided on landing. The accident report reveals that both the Air Accident Investigation Branch (AAIB) and the CAA consider that a lack of traffic information provided by the air-ground radio operator contributed to the accident and that regulations for the provision of an Air Ground Communications Service (AGCS), as provided at many training airfields, need to be tightened as a result. Industry experts are however questioning the AAIB and CAA’s conclusions, suggesting that tightening of regulations is unlikely to make any significant difference and that many airfield operators may struggle to afford the cost burden of the new regulation.
In August 2021 the pilot of a Boeing Stearman, returning the aircraft from maintenance to its home base, failed to spot a Cessna 182 joining the circuit and ended up landing on top of it, causing severe injury to the pilot of the C182. While both pilots claimed to have made the appropriate radio calls on entering the Aerodrome Traffic Zone (ATZ), and subsequent circuit position calls, neither pilot appeared to be aware of the other’s presence. The Stearman pilot had previously flown a touch and go on the active runway, before flying the left-hand circuit and making a curved left base turn. The Cessna 182 had meanwhile descended on the dead side of the circuit and positioned for a right base join.
The AAIB report then records: The C182 pilot reported that he continued toward final approach at approximately 600ft aal and when established on final transmitted “golf alpha golf final 22”. He reported that no radio calls were heard after his initial contact with Dunkeswell Radio and that he believed he was joining an empty circuit. Following a normal powered approach at approximately 70mph, the Cessna landed just beyond the displaced threshold, intending to turn off at the runway intersection. The groundspeed was allowed to decay and the flaps were retracted. With around 100m to go to the intersection, the pilot reported that he heard and felt what seemed like an “explosion” and then became aware of propeller blades rotating in front of his face. He recalled that the cockpit was filled with debris from the shattered windshield, shards of metal and splintered wood.
At the point the C182 was approximately one nautical mile from the runway threshold, CCTV footage showed the Stearman flying a curving left base leg, descending from downwind. The pilot was not aware that the C182 had joined the circuit and had heard no radio transmissions. The pilot reported that he made a radio transmission as he started the base leg, then again when established on final. He then heard a final call from another aircraft and, assuming it was an aircraft positioning behind him, made an information call: “November 27 final, close to threshold”. There was no response from the other aircraft, so he continued with the approach. CCTV footage showed that the Cessna had passed ahead of, and below, the Stearman before the Stearman had completed the base turn. Various witnesses reported seeing both aircraft on the final approach in very close proximity, “as though they were in formation”.
The Stearman pilot reported that the landing “didn’t feel right” and that the aircraft was not responding to control inputs. He applied power to correct what he felt was a drift to the left, then reduced power to idle. The aircraft continued to swing further to the left, off the runway and onto the grass. The pilot believed that the left landing gear had failed. Once the aircraft stopped, he looked down and saw that his aircraft was straddled on top of another aircraft, the C182.
The aftermath of the accident
Input from the air-ground radio operator appears to have been minimal during the unfolding scenario, with only one transmission made acknowledging the C182 pilot’s initial inbound call, with the radio operator providing runway and QFE information (air-ground radio operators are only allowed to provide information and are forbidden from giving instructions unless it’s critical to flight safety). There was no recollection by the air-ground radio operator of responding to the Stearman pilot’s calls. Both the AAIB and CAA consider that had the air-ground radio operator responded to all calls and made both aircraft aware that they were not alone in the circuit then the accident could likely have been avoided. Nevertheless, both pilots stated that they made appropriate radio calls when joining and while flying in the circuit. Witness evidence indicated that the following radio calls made by the pilots were heard, but it was not possible to establish the order of transmission:
· Stearman – Final call.
· Cessna – Final call.
· Stearman – second Final call with position update.
The accident report does not explain why the investigators think the pilots would have heard and acted on radio calls from the AGCS radio operator if they did not hear radio calls from each other. Unusually for this type of accident, the AAIB report also makes no mention of Electronic Conspicuity (EC) devices.
In tightening up the regulations, the CAA now emphasises that an air-ground radio must be staffed constantly during an airfield’s notified hours of operation and that the operator must be fully focussed on the radio and not distracted by other duties. The reality however is that the vast majority of airfields providing an AGCS do not employ fulltime radio operators, instead employing general operations staff who are tasked with multiple roles to keep an airfield running, alongside operating an air-ground radio. Paying staff to work an air-ground radio in isolation – especially when the airfield is quiet, such as on bad weather days – is a cost that some airfield operators have said they may not be able to afford. It certainly would appear impractical for a radio operator to spend all day doing nothing but monitoring the radio on a day when the weather is too bad for flying. There is also the fact that radio operators at certain UK airfields do not have a full view of runway approaches and so are unable to provide a visual verification of an aircraft’s position. And there are also a (albeit dwindling) number of non-radio light aircraft which may be operating perfectly legally at the airfield. Fundamentally, without radar or some form of surveillance oversight, an AGCS radio operator can never be fully confident that they have a complete picture of what is going on in an airfield circuit. The accident report acknowledges that even when an AGCS is being provided, it remains the pilot’s responsibility to ensure safe separation from other aircraft and to conform to published joining/circuit procedures, rather than relying on a third party, especially when that third party may not have the full picture.
The CAA’s updated guidance states in part:
Operators of Air Ground Communication Services (AGCS) are reminded of the guidance contained within CAP 452, and must adhere to all the below:
· The requirement to provide a continuous service during notified hours of operation.
· The importance of the expectation that the radio operator should be free from distractions, and
· The use of blind transmissions if no answer received outside of these notified hours
A number of airfield managers and operators have told FTN that if the CAA is going to insist on full-time air-ground radio operators they will instead by forced to turn their radios off and ask pilots to use the SAFETYCOM frequency instead, if the CAA allows them to. The CAA introduced the SAFETYCOM frequency in 2004. Assigned the frequency 135.475MHz SAFETYCOM can be used throughout the UK by aircraft operating in the vicinity of an aerodrome or landing site that does not have an air-ground frequency.
SAFETYCOM can only be used by aircraft at 2000ft or less above aerodrome or location elevation or below 1000 ft above circuit height. It is restricted to 10nm of the landing site and should normally be used only to broadcast the pilot’s intentions. There should be no response from the ground, except where the pilot of an aircraft on the ground also needs to transmit their intentions.
While switching to SAFETYCOM may work for some airfields, in certain cases the CAA may not allow the change to take place. The CAA judges an airfield’s required radio service based on a number of factors, including the number of aircraft movements, complexity of operations, and surrounding airspace. If an airfield is permitted to switch to SAFETYCOM it may also lose its ATZ, adding a further safety deficit. It has also been pointed-out that the change in procedures appears to have been enacted without any consultation with industry. Indeed, the CAA’s own announcement of the changes says that they have come about as a result of “… discussions held between the AAIB and the CAA”.
While the CAA’s intentions in tightening up AGCS regulations may be based on safety grounds, there are challenges that it is ‘gold-plating’ existing regulations and that the law of unintended consequences could potentially lead to a reduction in safety. While an ‘air-ground’ radio service has its limitations in its current format, it’s apparently the only format that many smaller airfields can afford, and the new, costly, requirements could effectively force airfields to switch to SAFETYCOM, bringing an end to a service that has worked well for decades. Meantime, those airfields that aren’t permitted to switch will have to bear the extra cost in employing dedicated air-ground radio operators, and this may only be affordable by reducing their published hours of operation, further eroding their income. Some GA airfields providing an AFIS information service already suffer daily closures to allow staff to take a break. The logical (and apparently unconsidered) consequences of the new CAA procedures could see this practice spreading to even the smallest airfields.
