ADS-B pit­falls

Flying - - Contents - By Sam Weigel

I had a few friends go to work in the chief-pi­lot of­fice at my last air­line, and they claimed that 5 per­cent of the pi­lot group created 95 per­cent of the prob­lems. I’m pretty sure that’s true clear across the avi­a­tion in­dus­try, and likely within gen­eral avi­a­tion as well. My key to fly­ing un­der the radar is to stay dili­gent, to keep my screw-ups small — and, when I do mess up, to read­ily con­fess and demon­strate that I’ve learned from it.

For most non­air­line pi­lots, “fes­s­ing up” might in­clude fil­ing a re­port through the Nasa-ad­min­is­tered Avi­a­tion Safety Re­port­ing Sys­tem. ASRS gives par­tic­i­pat­ing pi­lots a “get-out-of-jail-free card” for most un­in­ten­tional mis­takes, and in ex­change, gives the FAA insight into GA pi­lots’ prob­lem ar­eas. Ul­ti­mately, it al­lows them to de­sign a bet­ter sys­tem for us to op­er­ate within.

At the air­lines, we have a sim­i­lar but more ro­bust sys­tem called the Avi­a­tion Safety Ac­tion Pro­gram (ASAP). Pi­lots who dis­close hon­est mis­takes within a rea­son­able time frame are pro­tected from ca­reer-threat­en­ing FAA cer­tifi­cate ac­tion. A panel com­posed of an air­line safety spe­cial­ist, an FAA in­spec­tor and a pi­lot-union rep­re­sen­ta­tive con­sid­ers each de-iden­ti­fied case and has fairly broad pow­ers to re­quire safety im­prove­ments, in­clud­ing cor­rec­tive train­ing for the re­port­ing pi­lots. It also has the power to ex­clude a re­port if it de­cides the crew will­fully dis­obeyed pro­ce­dures or reg­u­la­tions, and the FAA can still pur­sue cer­tifi­cate ac­tion if it’s not a sole-source event (e.g., if the FAA al­ready knew about the in­ci­dent from ATC records or eye­wit­nesses). How­ever, the fact that the pro­gram re­quires pi­lot-union co­op­er­a­tion gen­er­ally keeps all par­ties act­ing in good faith, with a few highly pub­li­cized ex­cep­tions that were quickly rec­ti­fied.

This has re­sulted in most air­line pi­lots “buy­ing in” to ASAP. Most will very will­ingly sub­mit ASAP re­ports for events big and small — some­times quite small, to the ex­as­per­a­tion of

pro­gram ad­min­is­tra­tors. In my opin­ion, ASAP has done more to im­prove air­line safety than any other pro­gram since the adop­tion of crew re­source man­age­ment (CRM). A ver­sion of ASAP has even been ex­tended to air traffic con­trollers, and has helped cre­ate a more proac­tive safety cul­ture there than the old puni­tive “three deals and you’re out” sys­tem.

My air­line ca­reer co­in­cided with the adop­tion of ASAP at the re­gional air­lines, so I’ve been fil­ing ASAP re­ports go­ing on 15 years now — some­times for my own screw-ups, some­times for lurk­ing po­ten­tial “gotchas” I’ve no­ticed, some­times when the air­craft did some­thing wacko. I sub­mit­ted more ASAPS on the Mcdon­nell Dou­glas MD-80 than any other air­craft I’ve flown, most for that last rea­son. Mean­while, I’ve filed but a sin­gle ASAP re­port in the nearly two years I’ve been fly­ing the Boe­ing 757/767 — but it was a doozy. I even made our fleet’s monthly safety news­let­ter! The head­line: Gross Nav­i­ga­tional Er­ror. That cer­tainly sounds fore­bod­ing, doesn’t it?

My “gross nav­i­ga­tional er­ror” oc­curred over the frigid wastes of the North At­lantic Ocean, and was, in fact, a rather small de­vi­a­tion that never would have been no­ticed or re­ported in the “bad old days” of scratchy HF po­si­tion re­ports and non­radar con­trollers mov­ing pa­per chits across plot­ting ta­bles. Which is to say, a mere 15 years ago. The amaz­ingly busy North At­lantic tracks went straight from be­ing one of the most an­ti­quated chunks of con­trolled airspace in the world to one of the most mod­ern — and most mon­i­tored. The change is in­struc­tive to GA pi­lots as we face the ad­vent of ADS-B here at home.

Th­ese days, most air­lin­ers cross­ing the At­lantic are equipped with ADS-C (au­to­matic de­pen­dent sur­veil­lance-con­tract). Un­like ADS-B, which trans­mits air­craft data to spe­cial­ized ground re­ceiv­ing sta­tions, ADS-C trans­mits the same in­for­ma­tion across ex­ist­ing datalink net­works. Over re­mote ar­eas, th­ese net­works op­er­ate via HF ra­dio or (more typ­i­cally) sat­com. The sec­ond half of the sys­tem is the con­troller-pi­lot datalink com­mu­ni­ca­tions (CPDLC) sys­tem, which al­lows text com­mu­ni­ca­tion with ATC over those same datalink net­works. So those scratchy voice po­si­tion re­ports have been re­placed by au­to­mated up­links that trans­mit a vastly greater amount of data, all of it dead-on ac­cu­rate, and the few other com­mu­ni­ca­tions re­quired are usu­ally done via text mes­sage. It’s a sys­tem that is in­creas­ingly used in Europe, where fre­quen­cies in con­gested ATC sec­tors have fallen strangely quiet, as well as some de­vel­op­ing na­tions that lack ex­pen­sive radar cov­er­age but can now af­ford ADS-C and CPDLC.

On the night in ques­tion, I was in the right seat of a Boe­ing 767-300ER as we coasted out over New­found­land, Canada, and pre­pared to en­ter North At­lantic airspace. The cap­tain was in the bunk on his sched­uled break, the re­lief pi­lot fly­ing from the left seat. As we turned over our oceanic en­try point, the re­lief pi­lot en­tered an off­set of 2 miles right of course into our FMS

due to an Air­bus A380 ahead and above us, a stan­dard pro­ce­dure for wake-tur­bu­lence avoid­ance. I agreed that the off­set looked cor­rect on our nav­i­ga­tion dis­play, and the re­lief pi­lot hit the ex­e­cute but­ton. What nei­ther of us caught was that while the air­craft was al­ready “smart turn­ing” to the next fix, we were still a few tenths of a mile short of pass­ing the cur­rent way­point. Boe­ing 757s, 767s and 777s have a known bug in which the FMS does some very funky things when ex­e­cut­ing off­sets just be­fore way­point se­quenc­ing. It was a sim­ple mis­take on our part, but with se­ri­ous con­se­quences. The air­craft en­tered a right turn as though to in­ter­cept the off­set route, and then con­tin­ued turn­ing as if it wanted to head for Ber­muda!

Af­ter a mo­ment’s con­ster­na­tion, the re­lief pi­lot punched the head­ing-se­lect but­ton and got us turn­ing back to­ward our in­tended route. Only a few sec­onds

ding passed be­fore a loud re­sounded through the cock­pit — we were be­ing “paged” by Gan­der Oceanic Con­trol. We donned our head­sets and re­sponded on our HF ra­dio, and they gamely in­quired just where the heck we were go­ing. At this point I no­ticed that the FMS had also com­pletely deleted our next way­point! I ex­plained that we had suf­fered an FMS mal­func­tion and were re-en­ter­ing the cor­rect way­points and re­turn­ing to our course. We never got more than a cou­ple of miles off our route but had none­the­less com­mit­ted the grand pooh-bah of North At­lantic sins. You see, ADS-C doesn’t merely trans­mit po­si­tional in­for­ma­tion, but also the ex­act route in our FMS as well as se­lected au­topi­lot modes. As soon as our FMS con­tained a route other than our cleared one, we were guilty of a gross nav­i­ga­tional er­ror — the ac­tual phys­i­cal ex­tent of our de­vi­a­tion was irrelevant. Crews at my air­line have been dinged for merely en­ter­ing “re­minder way­points” that didn’t change the air­craft’s ac­tual route at all. Big Brother is very much watch­ing us out there.

Fes­s­ing up was easy — all three of us sub­mit­ted ASAP re­ports, even the cap­tain who was asleep in the crew-rest mod­ule at the time. My re­port in­cluded some of the con­tribut­ing fac­tors, such as the rel­a­tively high work­load while ap­proach­ing the oceanic en­try point, my lack of con­cen­tra­tion on proper se­quenc­ing as we passed the way­point and my for­get­ful­ness about the em­bed­ded FMS bug when ap­prov­ing the route off­set. The ASAP com­mit­tee ac­cepted all three re­ports with­out com­ment, turn­ing a po­ten­tial violation into a non­jeop­ardy event. A few weeks later, the flight-safety news­let­ter high­lighted our buga­boo. It wasn’t that we did any­thing uniquely stupid — quite the op­po­site, ac­tu­ally. ASAP re­ports re­vealed an uptick in sim­i­lar mis­takes, and it had been over a year since the Fms-bug memo had been is­sued, so our fleet cap­tain con­cluded that our crews could use a re­minder. This neatly il­lus­trates the con­tri­bu­tion that ASAP makes to a proac­tive safety cul­ture.

This in­ci­dent did get me think­ing, how­ever, about po­ten­tial con­se­quences for the U.S. gen­eral avi­a­tion fleet as it equips for the adop­tion of na­tion­wide ADS-B by 2020. Mind you, most ADS-B in­stal­la­tions will not trans­mit nearly as much in­for­ma­tion as a wide­body air­liner cross­ing oceanic airspace, but at a min­i­mum it will trans­mit ex­act po­si­tion, al­ti­tude and your air­craft’s N-num­ber. Clip a TFR, brush just inside Class B, fly only 950 feet above a “con­gested area,” and the feds will pos­sess in­con­tro­vert­ible ev­i­dence of your guilt be­fore you even land. The FAA points out that no ADS-B data has ever been used for en­force­ment ac­tion dur­ing the Cap­stone Project in Alaska, but I think we all know that the FAA of Alaska is not the FAA of the lower 48.

I’m not ar­gu­ing against ADS-B equipage, mind you; that ship has long sailed. But con­sid­er­ing that in the fu­ture many pi­lot mis­takes will be per­fectly recorded and po­ten­tially re­ported, I think it’s time for the FAA to re­con­sider some of its GA en­force­ment mech­a­nisms, lest pi­lots merely switch their ADS-B boxes off when­ever they me­an­der too close to the edges of le­gal­ity. Ex­plic­itly pro­hibit­ing the use of ADS-B data for en­force­ment ex­cept in egre­gious cases (where ex­ist­ing radar ev­i­dence would be suf­fi­cient) would be a good start. In ad­di­tion, I think the NASA ASRS pro­gram should be re­vamped to more closely align with the proven ASAP sys­tem, with a col­lab­o­ra­tive ap­proach be­tween FAA, in­dus­try and pi­lot ad­vo­cates, easy zero-risk re­port­ing and an em­pha­sis on train­ing and sys­tem fixes over puni­tive mea­sures. Get­ting GA pi­lots to buy into such a sys­tem as air­line pi­lots have would be a ma­jor boon to flight safety.

What nei­ther of us caught was that while the air­craft was al­ready “smart turn­ing” to the next fix, we were still a few tenths of a mile short of pass­ing the cur­rent way­point.

Most air­lin­ers cross­ing the At­lantic are equipped with ADS- C, while most of GA is start­ing to equip with ADS- B.

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