FLYING LESSONS for August 21, 2014 suggested by this week s aircraft mishap reports

Transcription

1 FLYING LESSONS for August 21, 2014 suggested by this week s aircraft mishap reports FLYING LESSONS uses the past week s mishap reports to consider what might have contributed to accidents, so you can make better decisions if you face similar circumstances. In almost all cases design characteristics of a specific make and model airplane have little direct bearing on the possible causes of aircraft accidents, so apply these FLYING LESSONS to any airplane you fly. Verify all technical information before applying it to your aircraft or operation, with manufacturers data and recommendations taking precedence. You are pilot in command, and are ultimately responsible for the decisions you make. FLYING LESSONS is an independent product of MASTERY FLIGHT TRAINING, INC. This week s lessons: A report was posted just before Oshkosh but received little publicity: Dutch Report on False Glideslope Signals The Dutch government s safety board wants to publicize the existence of false glideslope indications that could cause the aircraft, when coupled to the autopilot, to pitch up rather than down. The insights were gathered during an investigation into a pitch-up incident on a Boeing 737 in which the incident digressed until the aircraft s stick shaker activated [a stall warning indication tt]. The board wants pilots to understand the dangerous information these false glideslope signals can send to an aircraft s autopilot that might cause the system to operate in a manner opposite to what the cockpit crew expects. The report, published [in June 2014], focused too on the result of the unexpected pitch up. The resulting loss of airspeed may cause the aircraft to stall, the report said. The Dutch authorities said that while false glideslope indications are not new, until recently it was believed that even false signals would head the aircraft in the proper direction, down and toward the runway, just at a higher rate of descent. Further investigations revealed that four similar incidents have occurred in Europe, while 19 were found in a U.S. database, all at different airports and involving different operators. See We discussed this artifact of the Instrument Landing System with students 20 years ago while I was teaching in Beechcraft Bonanzas, Barons and Dukes at an international flight training corporation at the Beech Factory Airfield in Wichita, Kansas. This FAA diagram points out the hazard of false glideslope generation by ILS transmitters and how an airplane might encounter a much steeper, higher false glideslope if intercepting from above instead of below the correct signal. A few years later, while flying a Beechcraft Baron in corporate operations in the southeastern United States, I recall experiencing a false glideslope intercept while flying a coupled ILS approach. Flying into busy terminal airspace and arriving from a direction with relatively high terrain, I was higher than the published glideslope intercept altitude, and the nav radio apparently homed in on the glidepath above me instead of below. The Baron pitched up when I was expecting it to hold altitude for the intercept sensing, as best I could tell, the false 9 glideslope instead of waiting to intercept the true 3 path. Having taught this anomalous indication to others, after a brief moment of confusion I recognized the problem and disengaged the autopilot. Luckily, I was in visual conditions at the time and simply continued for a visual landing. Had I been in IMC (instrument meteorological conditions), I would have missed the approach and asked for vectors for another intercept.

2 This is why, I presume, most autopilots are designed to couple to a glideslope only when intercepted from below its possible that an intercept from above could begin from above the false glideslope also, and the autopilot might couple to this erroneous, very steep and screaming descent toward the ground. It s also why it s vital to compare your height and rate of descent when crossing the final approach fix (FAF) inbound on an ILS approach. Your altitude when crossing the FAF tells you you (or your autopilot) are sensing the glideslope and not some anomalous signal. Your rate of descent shortly afterward tells you you are following the proper glidepath if you re flying the steeper, 6 to 9 (and maybe even as much as a 15 ) false glideslope your rate of descent will be excessive if you (or the autopilot) keeps the glideslope indicator centered. If your autopilot pitches upward when you ve armed the ILS approach and are inbound toward the glideslope, disengage the autopilot immediately, hand-fly the airplane and assess the situation. If you have any doubt at all about what s happening, descend no further, report the situation to Air Traffic Control (ATC) and obtain an amended clearance to divert or try another intercept to the approach. If operational reality or ATC direction puts you in a position where you are descending into the glidepath from above, first realize that your autopilot will most likely fail to intercept the glideslope its operating logic prevents an intercept from anything other than below the glideslope. Second, hand-fly the airplane until you are established on glideslope. You may then engage the autopilot and couple it to the glideslope. But be ready in case it does not sense the glideslope long enough to couple for the approach. If you re forced to intercept the glideslope from above, you may be required to hand-fly the entire procedure. Comments? Questions? Suggestions? Mastery.flight.training@cox.net.

3 See bootcamp/update Debrief: Readers write about recent FLYING LESSONS: Reader Stuart Fraley writes about last month s LESSON about intermittently inoperative equipment: Thanks for a thought-provoking piece. As an owner/pilot, I find nothing more frustrating than intermittent failures. You know from your own experience that they often lead to multiple trips to the shop, where an avionics tech (it s always avionics that fail intermittently) generates a bill to say, I couldn t get it to fail. Bring it back when it s happening. Or they do find a problem but the act of opening the panel allows the entry of a new gremlin. Of all the ways to waste money, chasing gremlins is the most painful. I have a choice between a couple of avionics shops. One at the home drome is brand new and untested. One close by is highly reputed but very expensive and sometimes bumps little airplanes in order to work on jets. Others are reasonably priced but far away. So, in the words of one of my flying buddies, If it doesn t happen twice it didn t happen. If you have any tips on how to get to the bottom of intermittent failures, I d love to hear them. See I wish I did, Stuart. I ve been there too. I guess the best technique is to watch intermittent failures that cannot be duplicated in the shop extremely closely, and alter your operation as necessary to mitigate the risk of that device suddenly failing at an inopportune time. For example, if your glideslope indicator does not always center on the proper glide path, use it for advisory purposes only and fly to localizer or LNAV minimums, as applicable, until you can have it thoroughly checked and repaired. What you can t safely do is to simply hope it will work properly, when it s already demonstrated a tendency to fail. Reader Tom Allen continues: Another great article! With my airplane, I have had intermittent problems and since I know what they are, I know that I cannot count on the intermittent equipment when it is needed. One problem has always been that the intermittent problem will not reveal itself to the mechanic or radio shop. The second problem is that the repair person says, Oh yea, I know what that is and report that the problem is repaired and when it is not. And of course, anything can break and any time. I have gone months tracking down an intermittent problem. Then the problem is being able to communicate these issues to anyone who might fly the plane. So, let s say the intermittent problem is a pilot s Push to Talk switch. Let s say it has been in 3 times. What do you say? This article really resonates. I guess you d say that the push-to-talk switch fails repeatedly, and to make sure you have a handheld microphone accessible and plugged in (or ready to be plugged in) if needed. Also, review Lost Communication procedures in case the switch fails in the on position and its transmission blocks any radio frequency you might try to use. Frequent Debriefer David Heberling brings his perspective: In the airline world, there is so much redundancy built into each system that there can be many intermittent failures that do not jeopardize the safety of flight. This is not true of many GA airplanes. Glass instrumentation may lull some into launching with one screen or sensor inop. That is not really the purpose

4 of having multiple screens and sensors. That kind of redundancy is meant to get you safely on the ground following a failure of a screen or sensor. It is not meant to launch with such a failure. In my '73 vintage Bonanza, there is precious little redundancy besides two nav/coms with associated CDIs. For me, an intermittent failure qualifies as a hard failure, because I cannot risk having the intermittent or hard failure during IFR, or night flying, or both. The hard truth of everything aviation is that is an expensive endeavor. If you cannot afford to fix what is broken, you should not own an airplane. Any business that cuts corners like that is not a business anyone should step foot in. Then again, I am routinely surprised by what people will strap themselves into and fly. Thank you, David. Reader Tom Rosen opines about failures in automation management in hightechnology cockpits a LESSON from our July 17 th report: Frequent cause for an unsatisfactory outcome on an airline checkride was an attempt by the pilot flying to correct the autoflight system when it wasn't doing what was expected. For example, the autopilot didn't intercept the localizer. More often than not the pilot failed to correct the problem and the result was a continued deviation from the desired flight path. The proper solution was almost always to disconnect the autopilot and return the aircraft to the proper flight patch by hand flying the aircraft. In short, if it isn't doing what you want it to do, turn it off and fly the plane. See Great advice, Tom obvious, but seemingly alien to some pilots and training programs. Thank you. Reader Robert Thorson gives an historical perspective: Having flown in the days of steam driven gauges, rated on the GIV and then B757/767 when they first came out, and then back to B747 Classic, I may have a different opinion on automation. Recently I went to a TAA [Technologically Advanced Aircraft tt] school and in the last several years [have] flown the Cirrus, Diamond and G1000 C172SP. It seems to me that the root cause goes back to Human Factors. We are so accustomed to things working as advertised we rarely confirm a system operation after a switch position change. Old aircraft demanded this process because of unreliability. As time went on pilots were no longer taught this simplest of mitigation strategies. We can train this back into the pilot population. Whether you are fully automated or not the simple act of change in a flight deck should make the pilot note confirmation that the change did take place. Today s automation gives the pilot plenty of time to do this. Excellent reminder, Robert. Thank you. Reader Mike Busch replies to last week s LESSONS about failure to observe aircraft limitations: It's always a bad sign when a pilot turns to a passenger and says "watch this!" I first learned that lesson in the 1960s when I was working for a Fortune 500 company that owned a Lear 23. I was in the cabin on a business trip when the PIC leaned back and told the passengers "watch this" and then proceeded to roll the aircraft 360 degrees. I'm not sure, but I would venture a guess that "watch this" might be the #2 phrase that occurs immediately before air crashes. We all know what the #1 phrase is. See And reader Frank Palmer adds: I once heard, Watch this! from the pilot (an employee, who shall remain nameless) flying my Cessna 205 and I grabbed his arm and stopped him. It turned out he wanted to do a chandelle. We had a load of freight! Glad I stopped him. If I ever hear it again, the alarm bells are ready to go off in my head. Tony Crescimanno continues: I know of at least two people who sought other flight instructors after unsafe maneuvers were performed after the words "watch this" were spoken by their instructor. In both instances the students showed good judgment in electing to find other instructors for their flight training. Tony also addresses the recent LESSONS titled Don t Text and Taxi : To those who fail to see the dangers that are present when taxiing need only be reminded of Tenerife. Similarly, a number of years ago while taxiing in DFW there were multiple frequencies being used depending

5 on ones location on the field. I was given a clearance to cross an active runway where a 727 was on its takeoff roll. The 727 takeoff clearance was given on a different frequency from that which I had been assigned to monitor preventing me from knowing fully the conditions that existed. Constant visual scanning of the runway and immediate braking broke the chain of events. Taxiing is not the time to be heads down in the cockpit. See: While reader Michael Szczepanski returns us to the discussion of airframe limitations: On the Cirrus salesman and overconfidence, I beg to differ on the LESSON. From my copy of the private pilot PTS [Practical Test Standards] how different can it be in Australia [where the cited Cirrus crash occurred]? TASK: POWER OFF STALLS 3. Establishes a stabilized descent in the approach or landing configuration, as specified by the examiner. 4. Transitions smoothly from the approach or landing attitude to a pitch attitude that will induce a stall. 5. Maintains a specified heading, +/- 10, in straight flight; maintains a specified angle of bank not to exceed 20, +/- 10 ; in turning flight, while inducing the stall. And, from the description of events from the accident report: The PIC then took control of the aircraft and stated watch this. He selected 50% flap, rolled the aircraft into a left turn at about 25 angle of bank, reduced the power to idle, and raised the nose of the aircraft. The passenger in the front seat queried the use of flap and the PIC confirmed it was intended. As the aircraft approached the stall, the PIC pointed to the vertical speed indicator. As he did this, the right wing dropped rapidly and the aircraft entered a spin to the right. The PIC reported that at this time he performed his normal recovery procedure from this manoeuvre: maintained a neutral aileron control position, applied forward pressure on the control stick to pitch the aircraft nose down, rudders neutral and applied power. He reported that he moved the throttle lever forwards to increase power however there was a distinct hesitation in the engine response." The report then goes on to describe a horribly botched spin recovery. The PIC thought the sales prospect had put in right rudder, inducing the spin. Really, this report is of a pilot unable to perform a simple power-off stall, a maneuver student pilots should feel confident enough to practice solo. There is ignorance of proper spin recovery technique and it seems impossible the airplane was coordinated through the stall demonstration. Yes, watch this is a punchline in many an aviation joke, but this seems to be nothing more than another in a long list of basicairmanship-failure accidents. Any overconfidence by the PIC was just an overconfidence in his ability to perform as well as my Sport, Recreational, or Private Pilot candidates. In crashes it always seems to come down to three things: pilots don t exercise judgment, pilots don t fully understand advanced avionics and automation before committing to flight, and pilots aren t practiced enough in basic airplane handling. It sounds simple, but if we can merely address those three areas we could virtually eliminate fatal general aviation mishaps. What do you think? Let us know at mastery.flight.training@cox.net. Thanks for your ongoing articles in FLYING LESSONS Weekly. I need to send another voluntary contribution. Ever thought of asking readers in an reminder for annual contribution? -- Jerald Duncan Thank you, Jerald. The FLYING LESSONS supporters list includes many readers who have made two or more contributions to support continued delivery of these weekly reports as well as many who have made a single but also greatly appreciated donation. Financial support is always voluntary. Donations in excess of the costs of hosting and delivering FLYING LESSONS will go into other ways of increasing the quality and depth of these reports. See Be a FLYING LESSONS supporter through the secure PayPal donations button at Thank you, generous supporters

6 "The most important thing in flying is to learn your limitations and stay within them." -- Jimmy Doolittle, I Could Never Be So Lucky Again See Share safer skies. Forward FLYING LESSONS to a friend. Personal Aviation: Freedom. Choices. Responsibility. Thomas P. Turner, M.S. Aviation Safety, MCFI 2010 National FAA Safety Team Representative of the Year 2008 FAA Central Region CFI of the Year FLYING LESSONS is 2014 Mastery Flight Training, Inc. For more information see or contact mastery.flight.training@cox.net.