March 4, 2007
I had standardized procedures drilled into me early on -- an occupational hazard when your employer is the U.S. Air Force. In Air Force flight screening, flying off-the-shelf Cessna 172s we called T-41A Mescaleros, every flight was a series of standardized actions from preflight to the practice area to landing to shutdown. We knew what we were going to do before each mission, precisely what actions to take to set up each maneuver, and if we messed up, what we were supposed to have done to meet established standards. The eventual goal was to get as many of us as needed into military jets and mission-ready in a very short period of time.
I completed flight screening, but the "needs of the Air Force" sent me elsewhere. As a Minuteman ICBM launch crew officer everything was standardized, all actions literally done "by the book" using elaborate checklists we carried around in large three-ring binders. Strict standardization, down to the precise verbiage used in asking and answering questions, at least theoretically meant we could change crew pairings without notice and maintain the same level of performance. It was hard to argue such stringent standardization wasn't necessary, given what we were doing ... keeping 150 nuclear-tipped missiles ready to go at a moment's notice and, had the unthinkable actually happened, sent some or all of them on their way in correct response to a Presidential order.
What does any of this have to do with the much happier circumstance of flying a personal airplane?
Standard Operating Procedures, or SOPs, are any routine and repeatable way to accomplish a task. Whether you realize it or not, you've likely developed SOPs for much of your life, be it your morning routine from alarm clock to office chair, the route you drive to and from work, or the order you pick out items in the grocery store. SOPs naturally evolve for two main reasons:
- They're the simplest or quickest way to do something, and
- They cover all the necessary tasks in the proper order with little chance something is left out.
Put another way, SOPs minimize workload and ensure that the results of our inputs are predictable. That sure sounds like a good way to fly an airplane.
Example: ILS Approach
Here's an example of flying with an SOP. Flying an A36 Bonanza, I'm on vectors for an ILS approach. After briefing for the approach and setting up the cockpit I reference an approach checklist to make sure I've not forgotten anything. Given the final vector to intercept the localizer inbound I enter a so-called "approach configuration":
- Manifold pressure: 18 inches
- Propeller speed: 2500 rpm
- Mixture: As required for field elevation
- Flaps: Approach (12˚)
- Airspeed: 110 knots indicated
- Trim: Set
You might do things differently, for different reasons. And the technique obviously will differ with different models of aircraft, or even different versions of the same aircraft type.
From this point the airplane's performance is very predictable, so I can concentrate first on the intercept and afterward bracketing the localizer to establish a wind correction angle before reaching the glideslope. Alternatively this configuration provides predictable performance I use to monitor the proper functioning of the autopilot.
When the glideslope centers, I extend the landing gear and establish the proper pitch attitude for descent. If I'm using the autopilot, gear extension causes the airplane to maintain speed (and trim) as it pitches down to follow the glideslope. For me, this is all "SOP."
Two outcomes of using this SOP:
- I don't have to "make it up as I go," so my workload is much lower, and I'm mentally freed up for the navigation tasks without having to work hard on basic aircraft control.
- The resulting approach performance is extremely predictable, so I can quickly detect the effects of winds and turbulence and make minor changes to keep the needles centered.
Again, this sounds like a good way to fly an airplane: low workload, with high predictability.
One might also argue that a function of standardized operating procedures is to keep the airplane safely in the middle of the flight envelope. With rare exception most of us never need to squeeze the maximum performance out of an airplane. A good set of SOPs, well used, should ensure a safe flight. For example, one SOP might be to:
- Confirm, through multiple means, fuel on board before takeoff.
- Monitor fuel burn in flight, and regularly re-compute fuel remaining at the estimated time of arrival (ETA), and
- Divert and land for fuel if that computed figure ever dips below one hour's worth at cruise power.
Another SOP might be to:
- Extend retractable landing gear at the point you descend from or through traffic pattern altitude when flying a VFR traffic pattern.
- Confirm through multiple means the proper extension of the landing gear, and
- Re-confirm gear extension on short final, immediately going around if the gear cannot be confirmed to be down and locked.
If you follow both these SOPs every time, you won't fall victim to a fuel exhaustion crash, and you won't have a gear-up landing simply because you forgot to extend the wheels. Procedures like these keep you solidly in the middle of the airplane's safe flying envelope.
There are times, however, when you may need to fly closer to the edge of the flight envelope. Only by knowing what you must do to safely complete a flight task, and how the airplane predictably responds to changes in attitude, power and configuration, can you safely venture away from the safe, middle-of-the-envelope center. In other words, you can't safely experiment with new ideas and new techniques unless you are very firmly grounded in the SOPs.
Here's a real-world example: I'm flying that same A36 into a busy, tower-controlled airport, and controllers ask me to fly "best speed" to the outer marker ... a very common request. My approach SOP won't work because that's too slow for the turbine traffic behind me. Ultimately I want to transition to the approach SOP before I reach decision height so I can make a normal landing and clear the runway as quickly as possible. Since gear extension is necessary under this SOP, and putting down the landing gear is the quickest way to decelerate, I pick a power setting that in level flight keeps me just under the Bonanza's maximum gear extension speed. As I'm intercepting the glideslope I'll transition to the approach SOP and decelerate down the glideslope until I'm flying a normal approach. It meets the speed restriction and my safe-landing goals; I can accurately predict what the airplane will do so it is not a huge increase in workload that might distract me from landing safely.
In effect, I use my knowledge of the airplane's performance under SOP conditions to extrapolate what it'll do if I change any of the variables. I then experiment with a new plan, adjusting my inputs if actual performance varies from expectations. In effect, I develop a technique "on the fly," fine-tuning it on subsequent flights until it becomes a new "SOP" for use in this special circumstance.
Writing your SOPs
How can you go about developing a set of SOPs for the airplane(s) you're flying? Start with:
- Airplane checklists. Almost all airplanes have written normal, emergency and (in some types) abnormal procedures checklists in an Approved Flight Manual (AFM) or Pilots Operating Handbook (POH). These are the basis of a good set of SOPs for the actual operation of the airplane. There are several aftermarket sources for checklists for the most popular types of airplanes as well, often more detailed in some areas than those from the manufacturer.
- Supplemental checklists. Most additions to the basic airplane -- for example, autopilots and GPSs -- have a POH supplement that contains additional checklists. Educational programs should give you ideas for customizing your operations. There's nothing that says a specific checklist is mandatory, so most pilots eventually create their own SOPs that are a synthesis from POH, supplements and other sources.
- Regulatory sources. Weather minima, fuel requirements, oxygen use and all manner of other decisions are made easier if you compare your alternatives to those you have under aviation regulations. Remember that most rules were written because of an accident, or the strong likelihood of a mishap.
- Your own experience. What works for you? As you gain experience and knowledge, you'll undoubtedly update your personal SOPs to reflect your greater ability.
Your personal SOPs are a best-practices guide based on all available information. Commit them to print -- it'll make you think about how to fly your airplane for reduced workload and predictable performance.
Fly safe, and have fun!
Thomas Turner's Leading Edge columns are collected here.