A Twin & Turbine reader recently wrote about a harrowing experience:
I was almost involved in a midair a few weeks ago. I fly an MU-2 and was in IMC on an IFR flight plan, being given descent instructions by ATC into my home airport, Hazelton Regional (KHZL) in Pennsylvania. An aircraft came up on my TCAS [Traffic Collision Avoidance System]. He was VFR and not talking to ATC. He all of a sudden started a descent toward me. I turned. He turned. My TCAS showed our blips overlapping and a “0” for altitude difference. I guess he missed me by 50 feet. I mention this because an article on midairs, VFR flight into IMC, and usage of traffic displays might teach us a lot.
The Midair Record
“A near midair collision is defined as either an incident in which aircraft are less than 500 feet apart or…during which a pilot…feels that a hazard existed,” according to AOPA. Half of all midair collisions happen in the airport traffic pattern, AOPA reports. Of these, 80 percent occur during final approach within 400 feet of the ground. The most common scenarios resulting in an airplane collision are:
- Low-wing aircraft converging with a high-wing aircraft
- One aircraft overtaking another
- Collision on final approach at a nontowered airport resulting from loss of situational awareness
- Formation flying and air-to-air photography
- Complacency while en route
- Mistakenly taxing onto an active runway
The MU-2 pilot’s scenario may have included some elements from the list above but appears to have been a unique set of circumstances. Virtually all inflight collisions happen in day visual conditions – making the MU-2 pilot’s experience very unusual.
The IFR Pilot
The MU-2 pilot was flying a very capable twin turboprop. Given the FAA’s stringent special training requirements for flying the type (14 CFR 91 Subpart N) he is likely very well trained and proficient in the Mitsubishi twin.
TCAS is a system usually installed in larger airplanes. ICAO rules require TCAS in aircraft exceeding 12,600 pounds or authorized to carry more than 19 passengers. There is no TCAS requirement for aircraft operated under U.S. Part 91, while Part 135 requires it in airplanes with 10 or more seats. The MU-2 does not meet any of the conditions requiring TCAS, but it certainly could have been voluntarily installed.
TCAS was revolutionary when it first became available. But traffic avoidance systems like the almost-universally required ADS-B have caught up with all but the most advanced TCAS feature: the Resolution Advisory (RA). RA not only warns of an imminent collision threat but also gives the pilot audible instructions for avoiding it – directing a climb, turn or descent to avoid the conflicting aircraft. If an RA warning is given, the pilot is expected to comply and then advise ATC. Deviating from an ATC clearance by responding to an RA collision avoidance recommendation is treated the same as maneuvering to avoid collision visually – it does not rise to the level of an emergency and is not considered a violation of an IFR clearance, but it still requires a report to controllers.
Other traffic detectors – TCAD, TIS, ADS-B – display other-aircraft locations and relative altitudes (and with ADS-B, potentially more), but they do not provide an RA in the event of a near collision. Non-TCAS traffic detectors do, however, give us an additional tool to detect and maneuver around other aircraft in flight.
The VFR Pilot
We don’t know anything more about the VFR pilot than what the MU-2 pilot told us: an unknown-type aircraft not in contact with ATC was descending in IMC on a course that may have led to a collision had the MU-2 pilot not maneuvered out of the way. Interestingly, the pilot of the other aircraft apparently had the MU-2 in sight of its own traffic device, assuming it was in IMC as described, or he/she made a completely coincidental turn just as the two airplanes were coming together.
It’s possible that what the MU-2 pilot interpreted as instrument meteorological conditions were seen by the VFR pilot as visual meteorological conditions. If that was the case, the VFR pilot would have been required to maintain VFR visibility and cloud clearance requirements – generally three miles visibility and at least 500 feet below, 1,000 feet above and 2,000 feet laterally from clouds. In Class G airspace, this reduces to one-mile visibility and clear of clouds.
Most pilots are taught VFR minimums exist to provide the visual pilot enough outside references to maintain spatial orientation and avoid losing control of the aircraft. But in all but Class G airspace, the requirements are greater. Above 10,000 feet the separation requirements are greater still. The reality is that VFR minimums exist solely to prevent collision with an IFR airplane legitimately popping out of the clouds. That’s why the VFR limits are reduced in Class G airspace – without ATC control, it’s unlikely to see IFR operations under most circumstances (back to that shortly). At higher altitudes, IFR traffic is often flying faster, requiring a greater amount of time (distance) to see-and-avoid.
A few other possible scenarios for the VFR pilot in this near-collision – an airplane in distress, operating on a different ATC frequency combined with lack of coordination among controllers – but they seem unlikely.
Approaches at Nontowered Airports
The National Business Aviation Association (NBAA) has published, “Operating into a Non-Towered Airport?” The document is aimed primarily at the issue of closing contract control towers, turning Class D airspace into Class E and often Class G close to the surface, but the core issue remains collision avoidance. The guide states:
When approaching the airport, crews should also make a point to keep their eyes outside the cockpit in order to see and avoid other traffic and monitor the radio to help ascertain the positions of other aircraft in the vicinity. Pilots should also communicate their position and cooperate with other pilots in the area to establish the safest approach to the field, with the least potential for conflict with other traffic.
This is fairly basic guidance and is prefaced by this statement:
…pilots operating under an IFR flight plan to a…non-towered field will need to be prepared for the transition from the positive control environment of instrument flight when approaching their destination. These are skills that all business aircraft pilots should be familiar with but now will have to be applied at locations with newly closed control towers….
Well, yes, business pilots not only should but must follow the rules of visual flight in non-towered and uncontrolled airspace. See and avoid is the first and last defense, regardless of the aircraft type or performance.
FAA issued Advisory Circular 90-66B, “Non-towered Airport Flight Operations,” also provides basic guidance:
The pilot in command’s (PIC) primary responsibility is to see and avoid other aircraft and to help them see and avoid his or her aircraft. Keep lights and strobes on. The use of any traffic pattern procedure does not alter the responsibility of each pilot to see and avoid other aircraft. Pilots are encouraged to participate in “Operation Lights On,” a voluntary pilot safety program described in the AIM, paragraph 4-3-23, that is designed to improve the “see – and – avoid” capabilities.
Pilots should clearly communicate on the CTAF and coordinate maneuvering for and execution of the landing with other traffic so as not to disrupt the flow of other aircraft. Therefore, pilots operating in the traffic pattern should be alert at all times to aircraft executing straight-in landings…Instrument approaches should be particularly alert for other aircraft in the pattern so as to avoid interrupting the flow of traffic, and should bear in mind they do not have priority over other VFR traffic. Pilots are reminded that circling approaches require left-hand turns unless the approach procedure explicitly states otherwise. This has been upheld by prior FAA legal interpretations of § 91.126(b).
The Mitsubishi’s Approach
KHZL has three published approaches. The lowest approach minimums are on the RNAV (GPS) 28 approach (figure 1), which when flown as an LPV has a Decision Altitude (DA) of 1978 MSL…375 feet above the touchdown zone elevation (TDZE). Hazelton Regional is in Class G airspace, with Class E existing above 700 feet AGL (figure 2). This highlights an aspect of flying approaches at nontowered airports that many instrument pilots may not consider – in the last 325 feet of the approach above minimums, or from about 2,300 feet MSL on down, it’s perfectly legal for a VFR pilot to be just barely skimming the bases of the clouds and ATC may not tell you about it. Worse yet, many airplanes in this area are not required to have ADS-B or even a transponder.
I experienced this very thing on the first “actual” instrument approach I ever flew in the first IMC I’d ever experienced. As a newly minted IFR pilot, I flew a Cessna 182 on a 40-mile repositioning flight that terminated with an NDB approach into Boonville, Missouri. Breaking out on final approach, I saw another Skylane just ahead and below, crossing the approach course at a slight angle and somewhat faster cruise speed. The block letters spelling “Highway Patrol” atop the other airplane’s wing made it stand out in the murk. Early in my career I learned that the mix of IFR and VFR traffic on a marginal day requires vigilance.
From the MU-2 pilot’s narrative, he was higher than that and the conflicting airplane was higher still. But it reminds us of some collision avoidance techniques to use in and out of the clouds, whether or not the other pilot is legal at the time:
- Be obvious. Run strobes and/or navigation lights if they do not cause you disorientation in the clouds. It’s sometimes a challenge, but swap back and forth to the advisory frequency and announce yourself. Use distance, direction and altitude so non-IFR pilots will know where to look. For example, crossing JOVKU inbound on KHZL’s RNAV (GPS) 28, radio “five miles east, 3,500, descending straight in Runway 28.” If the other pilot is on CTAF this may help.
- Be predictable. Fly the procedure as published, including intermediate step-down altitudes. Someone who is familiar with instrument procedures will be expecting you at specific locations and altitudes and may be plotting to avoid you based on those expectations.
- Be vigilant. Legally near you or not, ATC may not be able to point out traffic as you fly an approach. Especially when breaking out on an approach at a nontowered airport, watch for VFR traffic in and near the pattern.
- Be ready to act. Instrument pilots get tremendous help from Air Traffic Control. But ultimately, the pilot-in-command is responsible for traffic avoidance. We all know that we must see-and-avoid when in visual condition even on an IFR flight plan. But even when in the clouds, if a traffic detection device shows a collision may be imminent, maneuver to avoid it and tell ATC later.
None of these suggestions will guarantee collision avoidance all of the time. But each of them will do the job at least some of the time.
Reporting a “Near Hit”
If you have a close call, reporting your experience might lead to improvements in the system. When in communication with a controller, report the incident immediately. A report will be entered into the FAA’s Near Midair Collision (NMAC) reporting program. Be specific as ATC will not interpret a casual remark as an official report. The pilot should state, “I wish to report a near midair collision.” You may also report by telephone to the nearest Flight Service Station or write the nearest Flight Standards District Office. You may also use the Aviation Safety Reporting System (ASRS) – operated by NASA – to report a near miss.