AIN Blog: AOA Must Be Here To Stay

 - March 14, 2016, 8:18 AM
A5
Icon Aircraft's A5 is a good example of angle-of-attack system design, with the gauge front and center in the pilot's view, and a logical depiction of AOA.

It is long past time that every airplane should come equipped from the factory with an angle-of-attack (AOA) indicator. 

Most new airplanes are already festooned with fancy glass display avionics, and adding AOA to an existing integrated flight deck is almost a no-brainer. At the worst, the airfamer would have to modify the wing slightly to fit a proper stall vane, but most of the work would be a simple software upgrade. And these software upgrades have already been developed and certified by avionics manufacturers, so it’s not that big a deal, nor should be it be that expensive. Even aftermarket glass can display AOA. Aspen Avionics is an excellent example of this and offers an AOA display that can be added to its Evolution display without any hardware; it’s simply a software upgrade.

The problem here is that airframers lack a coherent AOA strategy. Some aircraft manufacturers include AOA as standard on some of their airplanes but not others, some on all of their airplanes, some on none.

Why don’t all airplanes come with AOA now? After all, it’s a proven safety technology, and we know this from military aviation, where AOA predominates. Talk to a military pilot who has switched to civilian flying, and you’ll hear plenty of complaints about the lack of AOA in civil airplanes. Clearly they know the benefits of AOA and feel as though they’re missing an important safety tool when flying airplanes that lack this tool.

Here’s another reason, besides the fact that the FAA hasn’t mandated AOA installations (although it has made them much easier to certify): we as an industry aren’t convinced of the benefits. While loss-of-control accidents remain the biggest killer in this modern age, if you talk to industry pundits you’ll hear this refrain: “Well, there just isn’t any proof that AOA will help lower the accident rate. It’s nice to have, but will it really help keep pilots from killing themselves and others?”

It’s time to shoot down this hollow argument.

First, we know that AOA works; military aviation has proved it.

Second, pilots have no cockpit instrument that provides a direct reading of available lift, so they are constantly guessing by adding up various bits of information, including airspeed, bank angle, power, noise and gut feel (seat of the pants). This works most of the time, but without an AOA display there is no way to teach a pilot how to manage lift accurately.

Third, resistance by aircraft manufacturers to installing AOA systems in all of their new airplanes (and offering retrofits for older airplanes) reminds me of the industry push-back over the FAA rule that finally mandated installation of shoulder harnesses. It’s almost a crime that any airplane is legal to fly these days without shoulder harnesses, but the rule doesn’t apply if the airplane was delivered before it took effect. The shoulder harness rule came out in the early 1970s, decades after World War II experience with shoulder harnesses scientifically proved beyond any doubt that shoulder harnesses save lives.

While we do know that AOA systems are beneficial and have helped many military pilots, there is only one way to find out if the pundits who claim that AOA might be superfluous for the civilian world are wrong. Let’s get this over with and get AOA in every airplane possible, starting with new ones. We don’t need the FAA to tell us this is the right thing to do. And once we have more AOA systems installed in more airplanes, then we clearly see their value. And meanwhile I’m willing to bet that we’ll save some lives.

There is one fly in this ointment, however, and that is getting flight instructors to teach pilots how to use AOA systems properly. Instructors don’t always make sure pilots understand how to use every piece of equipment in the airplanes that they fly, and I don’t see that changing soon.

A friend related a sad example of this recently. He got checked out by two instructors at two separate light-sport airplane (LSA) rental outfits. Both airplanes are equipped with ballistic parachutes, another proven lifesaver. Yet during both checkouts, both instructors not only never said one word about the parachute, they also never made sure to remove the safety pin before flying. I know that there are still many pilots who don’t believe in ballistic parachutes, but instructors must discuss the parachute if equipped. Pilots can make their own decisions about whether to use it, but not to say anything about the system is a staggering omission. 

One final point: for AOA systems to be effective, they need to catch the pilot’s attention at the critical time. I’ve seen many types of AOA display, and they are wildly different and not always optimally placed. Icon Aircraft’s A5 is a good example of designers who understand this, and its AOA display is front and center in the instrument panel and large enough so that pilots will actually use it. 

Aspen’s AOA can be displayed much larger in one window on the Evolution display, which is good, although this has to be selected by the pilot.

The Garmin AOA display on its large displays (G1000 and higher) is somewhat small, a circular gauge at the bottom of the airspeed tape; a good first step, but more can be done.

What avionics designers ought to do is exploit the incredible power of their electronics and all this glass in modern cockpits and adjust the size of the AOA display depending on the severity of the situation. During normal operations, the display would remain in its original, perhaps small, configuration. As the wing approaches a stall, the gauge should grow larger to catch the pilot’s attention. In a stall, especially one that persists (such as those that have killed hundreds of airline passengers in recent years), the AOA depiction would take over the entire cockpit display and include a graphic that clearly shows the pilot to push forward on the yoke or stick. 

Comments

"Second, pilots have no cockpit instrument that provides a direct reading of available lift, so they are constantly guessing by adding up various bits of information, including airspeed, bank angle, power, noise and gut feel (seat of the pants). This works most of the time, but without an AOA display there is no way to teach a pilot how to manage lift accurately."
Dumbing down yet another basic skill.
I prefer to fly with a pilot that uses situation AND physical awareness to fly an airplane and not simply focus on another unneeded dial. If you think for a minute that installing one of these is going to keep the people alive that SHOULD be focused on angle of attack you're gravely mistaken. It's not going to keep the risk takers alive, and all the other pilots don't need it because they usually fly with considerable margins. "The AOA depiction would take over the entire cockpit display and include a graphic that clearly shows the pilot to push forward on the yoke or stick." Yeah...you're five hundred base to final and your display says push forward. The reason your instructed to "push forward" is because you have your stupid little eyes focused on the inside of the airplane and not outside! But go ahead...mandate another 1000 dollar part. Drive some more starters out of the market.

Matt Thurber's picture

Thank you for the comment. Of course, I too prefer flying with a pilot who is situationally aware and skilled at stick and rudder flying and knows how to manage the airplane's systems and avionics. But clearly what we as an industry have been doing for the past few decades isn't working; pilots still crash because they're stalling. Should we not change anything and accept the status quo or try something new and different and proven? Using an effective tool is not dumbing anything down, in my opinion.

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