Category: Flying

  • Colorado Mountain Wave in a Cessna 206 Turbo

    I thought I’d document my experience in Colorado Mountain Wave in my 206 on a recent flight from Idaho to Centennial, CO. The details are as follows:

    • Plane is a 206 Turbo with G1000 NXi and I imported the data from the data card into CloudAhoy which is how I made the video.
    • Wind that day was 270 at 35 KTS at 15,500 MSL which was my crossing altitude.
    • Crossing point was the East Portal which is a common crossing point for GA VFR aircraft. It’s kind of like a low wall with taller peaks north and south.
    • I think there was a high altitude temperature inversion that day but unfortunately did not confirm that and I can’t find a historic source for winds aloft to confirm this. Let me know if you know of one.
    • As I approached the rockies from the west, lenticular clouds were visible to the north and south with a cloud above me that may have been a lenticular cloud.

    I normally cross the East Portal at around 14,000 but after seeing the conditions for mountain wave I climbed up to 15,500 to give myself a bit more room. As I crossed the ridge I had the autopilot enabled and I encountered a descending column of air – perhaps at 1000fpm. The autopilot did its job and worked to maintain 15,500 which meant the plane entered a climb within that descending column of air and I watched my airspeed slow down from about 123 indicated to 97 IAS.

    I’d like to dwell on that for a moment. A friend of mine who is an accomplished instrument rated pilot was in a higher performance aircraft crossing the Sierras from west to east at night in IMC and encountered the same effect. A westerly wind was crossing the Sierras, which is also famous for mountain wave effect and creating a downward flow on the leeward side. The autopilot tried to maintain altitude and the plane slowed down enough that when he finally noticed it really got his attention.

    I was told this story in person and reading between the lines this left a strong impression on him. I think part of the reason is that in the higher performance plane his stall speed was fairly high, so the potential to have the autopilot drop the airspeed enough to stall the plane was higher. I don’t know if his plane had Garmin ESP. Mine does, and it will nudge the nose down if the plane appears to be entering a power on stall. I plan to verify this.

    Once the airspeed crossed 100 kts and continued to drop, I turned the AP off and pointed the nose down. At this point the airflow across the ridge and in the leeward side at 15,500 was laminar – very smooth. You can see this in the video below if you look at the G meter in the top left.

    As I descended and moved further away from the ridge, I think what happened is I moved below that laminar flow. As I got out into the foothills and at around 13,700 MSL which was 5,200 AGL I was hit with moderate turbulence. In FAA terms, moderate is passengers screaming and crying and severe is the airframe at risk of taking damage. I’d say I was on the high side of moderate.

    I experienced plus 1 G (or plus 2 if you want to nitpick and point out that 1G is at rest) and negative 0.5 to 0.7 although I haven’t verified this. You can see the G meter in the video. The aircraft can handle +3.8G and -1.52 flaps up.

    I got one thing right and made two mistakes. Crossing at a much higher altitude and maintaining that higher altitude than normal give me plenty of room AGL to recover from a stall/spin scenario. The first mistake was to descend at an airspeed that was far too high given the potential for turbulence. I hit the turbulence at around 150kts indicated and within a second due to wind shear the ASI jumps to 163.

    I pulled power at that point and gently nosed up to avoid increased G loading on the airframe, but was doing everything I could to rapidly reduce my speed. The turbulence was short and sharp. The G loading wasn’t particularly high in terms of what the airframe can stand at my weight and balance, and given that I’d burned most of my fuel, but the short sharp nature of it was of real concern.

    I then made the second mistake which was to slow down too much. I think I got as slow as 83 indicated, which is way above the published clean stall speed of 62 KCAS but given the wind shear, I should have kept it at maneuvering speed which ranges from 106 KIAS to 125 KIAS with the lower speed being for lighter aircraft loading. I was probably around 110 KIAS given my fuel and load. 105 KIAS would have been a safe speed to do the entire descent.

    I was talking to Denver Departure so called them up and gave them a moderate to severe turbulence PIREP which I revised a couple of minutes later to Moderate.

    Right before I encountered the turbulence I saw my VSI indicate I was entering an ascending column of air. It’s hard to tell how fast it was ascending because I nosed up to reduce airspeed. My VSI peaked at 3100 fpm. But I then encountered a descending column of air which was also 3100 fpm with pitch level. That’s around 31 knots of descending air, to put it in perspective. My tail wind at that point was 40 kts based on the difference between TAS and ground speed via CloudAhoy. So 40 knots horizontal and 30 kts downward. Fun stuff.

    This effect is due to a laminar mountain wave flowing over the rockies and extending in a repeating sine wave over the plains. But underneath that laminar flow you get a strong rotor effect which can do severe damage to aircraft.

    Around the same time a TBM reported severe turbulence within KAPA’s (Centennial’s) Delta which is quite far east from the foothills. As I approached KAPA the turbulence became very intermittent but I can see how a rotor might have reached down into KAPAs Delta and knocked that TBM around given what I had experienced from 13,700 down to 11,000.

    I’ve done a fair amount of reading about mountain wave, but that doesn’t prepare you for real world experience – and unfortunately in my case the knowledge didn’t bed down enough for me to slow down to maneuvering speed on my descent, which of course I’m really beating myself up over.

    My takeaways are as follows:

    • Avoid the leeward side of the Rockies in mountain wave conditions.
    • If you absolutely have to be in the lee of the rockies in these conditions (I can’t imagine why – maybe research, maybe a mistake), give yourself plenty of altitude, slow down to whatever your POH says is turbulent air penetration speed, and lock everything down. You’re going to get beaten up. I was rolled a few times fairly aggressively too – to about 45 degrees before I caught it each time. Very quick rolls.
    • Absolutely do not head westward towards the lee side of the slope with ascending terrain, even if you have a turbo. You’re liable to not notice your reducing AGL altitude and if you encounter a severe downdraft you could easily get smacked into the mountain. We recently lost a CAP piston single in the lee of one of the slopes. It looks like they entered the lee at only 500 AGL with 35 kts over the ridge.
    • This time of year in fall/winter/spring we frequenty see mountain waves, so I’ll either avoid crossing the high Rockies, or try to time it when winds aloft are less than 20 kts which sometimes happens in the mornings.

    Here’s a video of the telemetry imported into CloudAhoy which provides a simulation of the flight. I’ve added a narration. Clearly this is designed for interested aviators and not the YouTube crowd. 🙂

    Further reading:

  • Briefing Something Mission Critical When Failure Is Not An Option

    I started my career in IT operations moving to London and working on initially Coca Cola’s infrastructure, and then moving into investment banking and working on trade floor infrastructure. This was after being based in South Africa and doing quite a lot of work for DeBeers on e.g. the most productive diamond mine in the world at the time. I absolutely loved working on mission critical systems. Love the rush. Loved at 4am being one of a small team doing a complex deployment on a sometimes multi-billion dollar business, where failure was not an option.

    So failure not being an option is something that has fascinated me. I’m an instrument rated pilot. I fly a Cessna 206 in what in aviation is referred to as single pilot IFR – meaning that I’m flying on an instrument flight plan in bad weather i.e. in the clouds, and there’s only one of me in the cockpit. It’s some of the most demanding flying one can do in terms of cognitive workload. And of course failure is absolutely not an option.

    In instrument flying we use approach plates to conduct an instrument approach. The approach phase is one of the busiest times in the cockpit along with doing an instrument departure procedure. The approach plate is a one page easy to read summary of several critical pieces of information, like what my frequencies are, what my critical altitudes are, what path I’m flying and what to do if, when I get to the runway, the clouds are so low that I can’t see it and I have to execute a missed approach.

    There’s a technique we use called “briefing the approach” which is really designed for a two pilot environment, but us single pilot IFR guys use the same technique. You’ll do a read-through of the instrument approach plate before you actually start flying the approach, and you’ll do it at a time when you’re not as busy as you’re about to be. Starting at the top you’ll read through items like frequencies, navigational fixes, minimum altitudes, missed procedure and so on.

    I can’t share the approach plates I use because they’re published by Jeppesen and are copyrighted, but here is the FAA plate for the approach on Orcas Island where I live, that I fly quite a lot.

    The briefing from the top of the plate will go something like this:

    • OK so the approach we’re doing is the RNAV runway 16 at Orcas Island
    • Our approach course is 193 degrees
    • Airport elevation and touchdown zone elevation are 35 feet
    • AWOS frequency [for the weather] is 135.425 and we’ve already given it a listen and have the weather
    • Whidbey approach frequency is 118.2 and we’re already talking to them and we’ll be switching to Victoria on 132.7 soon and I have that dialed in
    • Once we’re on the approach they’ll switch us to the advisory frequency which is 128.25 and I have that ready.
    • Our final approach fix is CALBI which we’ll cross at 1900 or above.
    • We’re doing an LP approach and our minimums are 340ft and I’ve got that dialed in.
    • Our missed procedure is…..

    [Side note: If you’re instrument rated, don’t nit pick my briefing here. It’s designed to be parsable by non-pilots and is for illustrative purposes only.]

    And so it goes. It’s a relatively quick process and it’s more concise then I’ve described here because there’s some jargon used.

    As a single pilot flying IFR (instrument flight rules) you literally say the briefing out loud to yourself before flying the approach. This technique is one of the many that aviation has come up with to mitigate the weakest link in aviation, which is the human being at the controls. In general aviation (non scheduled flights like I fly) around 78% of accidents are caused by the human. And so aviation spends a lot of time coming up with techniques like this to mitigate the risk of the human making a mistake.

    Surgery has a similar technique called the timeout. The timeout is essentially the surgical team “briefing” the procedure. This includes basic items like the patient identity and the surgical site. It’s to prevent fundamental errors like wrong site, wrong person or wrong procedure errors.

    I’ve incorporated this concept into my business (Defiant Inc which makes Wordfence) and my personal life. If I’m about to hitch a 10,000 pound trailer to my truck, take it into a ferry and go do a bunch of stuff on the mainland, I’ll brief it with my wife to make sure we haven’t missed anything. Yeah – I know- that makes me sound like a bureaucratic pain in the ass, but we’ll just spend a couple minutes talking through what we’re about to do and whether we have everything we need.

    If we’re about to do something complex or mission critical at work I’ll brief it with the team. They don’t realize what I’m doing most of the time, but I’ll describe it as “briefing” the thing and we’ll just talk through what may seem to many on the call as some obvious details. Sometimes something will fall out that we need to address, or we’ll go deep on an issue.

    When you’re doing something that is mission critical where failure is not an option, consider briefing the thing. Just talk through what you’re about to do and the pertinent details. It’s really just a mental shift where you’re fully dedicating your mental capacity to thinking about what you’re about to do and the details, rather than assuming you’ve got it all figured out. And then when you get busy or are under pressure, you’ll have all the data and procedures stored in your short term mental cache ready to go.

    Footnote: “Failure is not an option” doesn’t originate from NASA. It actually comes from the film Apollo 13. But from what I’ve seen, aviation has enthusiastically adopted the phrase.

  • The FAA needs to get their hands dirty to enable UAV innovation

    In the 1970’s and much of the 80’s, passengers on commercial aircraft would occasionally experience the joy of the ‘holding pattern’. Having their plane stacked with other planes circling in a spiral due to a delay at a destination airport. Planes would circle sometimes for hours, with priority given to those about to run out of fuel.

    Then in 1981 the FAA used a ground delay program (GDP) for the first time during an air traffic controllers strike. The advantage of keeping airplanes on the ground at their departure airport was immediately obvious: passengers are just as unhappy, but they’re safer and the aircraft isn’t burning fuel at 161 lbs per minute (or 73kg per minute for the 767) in a holding pattern. Today the ground delay program is run by the  Air Traffic Control System Command Center, in Warrenton, Virginia which coordinates commercial flights around the USA and Canada and implements a GDP for destination airports if their arrival rate drops below a threshold.

    The FAA is catching a lot of heat for their delay in implementing UAV (or drone) legislation. The drone pilot part of me sympathizes with the public and I think what is particularly frustrating is that a small handful of commercial operators have actually been granted licenses to operate giving them an unfair advantage over other operators. The article in the Denver Post today probably stung a bit among unlicensed operators when one of the already-licensed operators described the FAA’s pace as “about where it should be”. Sure, it works for them.

    But the private pilot part of me – and the aviation history enthusiast part of me is sympathetic towards the FAA’s plight. Make no mistake, I think we should bringing as much public pressure to bear on them as we can. In the legislative environment we’ve inherited that’s the only way anything will get done. But this country has a long and storied history in traditional aviation and we have achieved a remarkable improvement in safety by creating well engineered solutions for specific problems. A glance at the chart below showing safety from the 70’s until 2012 illustrates that. [Source: The Economist on air safety and MH370]

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    The FAA is not asleep at the switch – they are continuing to innovate and improve safety and efficiency with the rollout of the Next Generation Air Transport System which started in 2012 and is due to complete in 2025. Part of this rollout was support for ADS-B which is just about complete. This remarkable system gives everyone including hobby pilots like you and I the ability to buy an $800 transceiver, attach it to our iPAD and get real-time traffic and weather data as we fly anywhere in the USA while sharing our own position with other pilots and air traffic control. Previously you had to buy expensive avionics systems and a subscription to a commercial provider’s satellite feed.

    Unfortunately we are stuck, while we wait for formal FAA legislation, using an FAA advisory circular (91-57) that applies to radio control model aircraft as our legislative guide. It says, don’t fly near populated areas, don’t operate near spectators until you’re sure your aircraft works, don’t fly above 400ft, don’t fly near an airport without notifying them, give way to full scale aircraft, ask the FAA for help if you need it.

    Comparing a model aircraft to a drone is like comparing the Wright Flyer to a 767. One has wings and an engine. The other has GPS, avionics, autopilot, gyros, accelerometers, real-time ground station connectivity, real-time logging for later analysis and flight modes ranging from fully-autonomous to the pilot having an advisory role with the computer taking over when needed – to fully manual. (I am comparing most newer commercial long range aircraft with the IRIS+ by 3DRobotics for $750).

    Most drone innovators are very excited by the prospect of being able to fly their aircraft out of sight autonomously. Whether it’s Amazon wanting to do package delivery, a survey company wanting to offer services to farmers or me wanting to deliver beer to my friend a few blocks away. Autonomous flight is the most useful aspect of drones and they are very very good at it. I can go outside right now and get my IRIS+ to fly 3 miles away at 390 feet, descend to 60 feet, point the camera on gimbal at my friend’s house, circle the house in a smooth spline navigation path as it films the home, ascend back to 390 and return to me and I can get telemetry via an excellent 900 mhz transceiver from the drone the whole way and even take over manual control if I feel the need. But that’s not allowed because the FAA won’t let us fly out of sight until they make laws which may simply formalize the fact that hobby drones can’t fly out of sight.

    The USA is filled with tech innovators that are salivating at the prospect of trying out new things with drones – things that may drastically improve our quality of life and safety. I’m reminded of the horrific King5 news chopper crash a few years ago in Seattle which killed 2 and burned a third victim. Today that job can be done by a drone costing under $2000 – filmed in 4K video, gimbal stabilized with real-time first person view as film is being shot. With an amateur radio FCC license the operator can legally boost the drone telemetry and video signal from 0.2 watts to 10 watts with a high gain antenna and increase range to the point where battery life is the only issue.

    But autonomous flight innovation of that kind is banned and the only laws we have to guide us right now are an advisory circular relating to model aircraft and public statements by the FAA. Some operators are saying “to hell with it, we’re flying” as is the case with Texas EquuSearch. The search and rescue operator was issued a warning by the FAA, they then turned around and sued the FAA and a federal court threw out the case saying that the email the FAA sent EquuSearch did “not represent the consummation of the agency’s decision making process, nor did it give rise to any legal consequences.”. EquuSearch have interpreted this as the FAA having no jurisdiction and so they have decided to continue flying.

    In my view the FAA must be very careful to not treat drones like manned aircraft because they risk band-aiding the situation and crippling innovation. They need to look at the modern air space systems and innovations that have worked there and then assess drones as unique and completely different entities that happen to exist within their jurisdiction. I think giving everyone from hobbyists to commercial and government operators the ability to perform out-of-sight autonomous flights is a very important and necessary goal if they are to be an enabler of innovation rather than being a crippling force that ensures we aren’t competitive in this new arena of aerospace.

    It is essential that this country (the USA) maintains its dominance in aerospace and we worked incredibly hard to get to where we are today – from the Wright Flyer to breaking the sound barrier, to getting our asses kicked by the Soviets when they made it to space first, but we regained the lead by getting to the Moon first. Then on to Stealth technology and military UAV’s. We’ve managed to stay out in front. To do this we need to enable the private sector to conduct research into autonomous flight and the private sector includes individuals and small groups of entrepreneurs. We need to enable them and we need to do it as fast as possible.

    To allow autonomous flight I would propose a system similar to DUATS which pilots today use to file flight plans. The FAA should create a system whereby drone operators at defined levels of competence and commerciality are able to file a flight plan before flight. The plan would include waypoints with latitude, longitude and altitude. The flight plan would be filed an hour before flight and define a window for the flight. It would also be approved on the spot or rejected due to a conflict with another plan, temporary flight restrictions (TFR’s) or an airspace conflict.

    I would suggest that a system like this could be used for autonomous flights under 400 ft in open areas. With additional licensing operators should be able to enter our national airspace system which starts at 500ft and this may include additional equipment like an ADS-B transceiver. And with further licensing, as with the current pilot requirement of an instrument rating, pilots may be able to complete autonomous flights above 18,000 feet.

    To truly enable innovation in autonomous flight, the FAA can’t simply bandaid the existing system. They need to be an enabler and create new products and services to support drone operators and ensure that, as we have with manned aircraft systems, innovators are able to improve safety, efficiency and quality of life with unmanned aircraft.

  • Instrument failure after takeoff and becoming an outside-in pilot.

    This is my first post as a relatively newly minted private pilot (about 4 months ago). The learning curve has been steep and it’s the kind of thing that humbles one, so I haven’t felt the sense of entitlement that one needs to write. But I am beginning to spot a few things that may help others, so here goes:

    I was taking two friends for a cross country from Centennial Airport (KAPA) to Rocky Mountain Metro (KBJC) and had a learning experience. Preflight went great, the Cessna 172SP I was flying was in great shape and a nice plane with airbags and great avionics. I taxied to 17L  for departure, cleared for takeoff, took her up to 60 knots before rotating because we had 3 people on board with full tanks at 6000 ft with a 180HP plane, so I wanted plenty of speed as I rotated.

    Climbing out KAPA tower told me to turn west, cross over I25 and then continue on-course. I looked at my gyroscopic magnetic heading indicator and west was to my left and the I25 was to my right. I got that sinking feeling of “something’s wrong” without consciously realizing what it was. If you fly out of KAPA you probably already know what happened.

    I radioed tower with “Tower just to confirm, you want me to turn left? and then cross over I25 and on course?”. Reply: “No, turn right and then on course to Metro”. My spatial orientation kicked in and I turned right and all was well.

    My vacuum powered magnetic heading indicator had seized. I had set it correctly before takeoff. I had plenty of vacuum on the gauge. All other instruments were fine, but that one instrument seized in exactly the opposite position to where it should be pointing. I realized that as I turned right, checked my magnetic compass was working, and started thinking about whether I should turn back or continue. I decided to continue and my subsequent reading of FAR 91.205 looks like I made the right call. Required equipment for VFR is a “magnetic direction indicator” which means I was OK just using a magnetic compass.

    Besides some serious turbulence at Metro on landing caused by a strong mountain breeze, the rest of the flight was fun and uneventful.

    So my takeaway from this is to become more of an “outside-in” pilot rather than an “inside-out” pilot. Meaning that I need to focus on orienting myself using external landmarks and the attitude of the plane and then verify with instruments, rather than focusing on instruments and then verifying with external landmarks and plane attitude.