Avoiding Enroute Wake Turbulence

Simple Techniques Critical to Safety

On January 7th, 2017, there was an amazing incident that occurred over the Arabian Sea. An Emirates A380 “Super” passed 1000 feet overhead of a Challenger 604. A short time later (1-2 minutes) the aircraft encountered wake turbulence sending the aircraft in uncontrolled roll turning the aircraft around at least 3 times (possibly even 5 times), both engines flamed out, the Ram Air Turbine could not deploy possibly as result of G-forces and structural stress, the aircraft lost about 10,000 feet until the crew was able to recover the aircraft exercising raw muscle force, restart the engines and divert to Muscat.

Lufthansa A380 westbound over Newfoundland after passing within 1 mile and 1000 feet of the author’s flight path.

Now, many articles are popping up regarding the wake of an A380 — mainly talking about what we know and what we still don’t know about the wake turbulence produced by the behemoth. Practically speaking, however, we don’t need much research to inform our decision as pilots to use an abundance of caution when crossing near the flight path of any other aircraft. Many of us have had wake encounters from much smaller airframes than an A380 to teach us valuable lessons on the topic.

What can we do to ensure we don’t end up like the Challenger 604 did? (See the dramatic before and after pics here.) Try to employ these simple techniques to strategically avoid a bad wake encounter:

1. Pay Attention to TCAS/ACAS Info

Sometimes we can find ourself numb to TCAS information. Our airspace can become so busy, so dense with surrounding traffic, that we tend to “tune out” the information on the primary nav display. Granted, we should work hard at “see and avoid” airmanship all the time. Except, we cannot “see” wake turbulence. Additionally, current TCAS displays in use on most commercial aircraft only display altitude, relative position, and climb trend information. Aircraft type data is currently unavailable, however with further use of ADS-B technology, as well as development of the ACAS-X technology, it may become a feature. (ACAS-X will basically be next-gen TCAS-IV using ADS-B after the year 2020 FAA mandate for ADS-B).

Another busy day in SFO! VOR 28L approach? Yikes!

Strategic use of TCAS includes actually paying attention to what is near you. Any targets within a 10nm radius of your position and 1000-2000 feet above your altitude should be your primary concern. Targets of that meet this location and altitude criteria that will either converge, cross, track ahead or pass opposite direction same track should sound the alarm bell for you to be on guard for their wake.

2. ATC Traffic Callouts – Better Late Than Never

Traffic callouts by ATC don’t always come, and when they do, it’s probably just in the nick of time for you to see the traffic zip on by. As we get more use out of CPDLC and aircraft addressable communication systems, traffic calls will become a thing of the past in the enroute environment, and we will have TCAS/ACAS only to back up our eyes. Until then, pay close attention to the ATC callouts you do receive. Unlike todays TCAS, they do give the aircraft type. Super handy indeed. When you hear, “…traffic, 10 miles, 2 o’clock crossing your path 1000 feet above…” or something similar, even though the collision danger is low, the wake danger may not be. By the time you eat up that distance, the wake has settled 1000 feet to your altitude. Use these ATC calls to not just look out the window and pick up your scan, but also to do some strategic thinking on where their wake is and where it could be in the next 1-2 minutes. When you encounter wake after passing traffic that was called out to you (and especially when it wasn’t) you need to let ATC know about it.

3. Course Deviation May Be Necessary

Perhaps its because we get into this groove of precision following magenta lines in the sky. We focus on our ANP to meet RNP standards. God forbid we drift off course! LNAV is a godsend! Fact is, we can (and we do) deviate off course all of the time. Especially for weather. Many times per ATC’s bidding. So why not make some course changes to avoid a wake encounter? Best practice here is to get oblique to the flight path of the aircraft you are avoiding. Perhaps that’s a 30-45 degree turn, holding that heading for about 5 miles upwind of the flight path you were on, and then going direct to your next waypoint again. Coordinate with ATC as you are able, but remember that your deviation authority can come in handy here if you think the need is dire.

Another technique that is widely used, and is an international standard, is Strategic Lateral Offset Procedures (SLOP). It is used predominantly over Class II navigation and ETOPS routes over long reaches of ocean. SLOP is a recommended procedure, for example, in the North Atlantic Track System. Once established on your designated route (your cleared “track”), SLOP means flying an offset to the right of course, up to 2 nm. Left offsets are not allowed, and no more than 2 nm. By utilizing TCAS/ACAS, you can typically see what offset the proceeding flights are running, and choose yours accordingly. In addition, in most airspace where SLOP is approved, calling other flights to coordinate offsets is recommended on VHF 123.450 MHz.

Question: What techniques and actions do you take to avoid enroute wake turbulence? You can leave a comment by clicking here.

Please note: I reserve the right to delete comments that are offensive or off-topic.