Different Types of Preflight Inspections

by David J Fill II @davidfill

Have you ever walked out to your favorite Cessna 172 sitting on the rental line and had someone else tell you “it’s all set to fly,” at which point you walk around the plane from a bit of a distance, hop in and go?  Believe it or not that’s the way airline, charter, and many corporate operations work every day and their safety record is generally better than the average eagle-eyed General Aviation pre-flight expert.

You’ve probably sat in the boarding area at the airport looking out the window to the ramp and seen a first officer walk around an airplane with his hands in his pockets as though he’s on a leisurely walk in the park. That pilot is responsible for equipment much more expensive than your 172 and many more lives than could possibly be jammed into your average GA airplane. He probably has a lot more training and experience than your average GA pilot yet it almost seems like he doesn’t take the preflight seriously. The reality is that in certain areas of Part 121, 135, and 91 flying the preflight inspection is a shared team effort and the depth of such an inspection depends on many factors.

Preflight inspections are boring. The preflight inspection is probably one of the first things we learn about as student pilots and the importance of conducting a thorough inspection is ingrained in our training from Day One. The preflight is simply a means to an end. No one heads out to the airport excited to crawl around under the plane, get their pants dirty, and probably smack their head a time or two – we are there to fly and that’s what generally receives the majority of our attention.

The detail and depth of a preflight inspection can vary from day to day based on the type of airplane we are flying, where that airplane is parked, and even whether recent maintenance has been conducted. I will leave Part 121 Airline operations out of this discussion because that topic alone could fill several pages. Lets talk about our preflight attitude or mindset for renters/flying clubs/partnerships, individual owners, Part 135 or Part 91 corporate operations, and airplanes fresh out of maintenance.

Renters/Clubs/Partnerships
You’re probably wondering why renters, clubs, and partnerships are all thrown into one group. One of the positive aspects of owning your own aircraft is having the privilege of flying the same plane with the same equipment all the time without worrying about the abuse an airframe on the rental line takes. The truth is that if anyone other that you have been flying the airplane – including a partner – it should be treated virtually the same as an airplane off the rental line. You probably know your partner(s) well and trust them along with their flying experience but in reality have no way of knowing what happened to that airplane since you last sat in the left seat.

As a pilot in this group you really have no way of knowing what happened to the airplane prior to grabbing the keys. It’s not uncommon for a renter to head out to a plane parked on the line and find the tips of the prop slightly curled over due to a minor prop strike – the previous renter may not even have been aware of the damage. We all can probably remember our first couple of landings as a student pilot and therefore understand the abuse that trainers take. Obviously this is all very dependent on the type of aircraft but particular attention should be paid to structural damage including wrinkled aircraft skin, hangar rash, and prop damage as well as flat-spotted tires, gear issues, brakes worn beyond limits, and loose or smoking rivets or screws.

As far as the interior inspection goes make sure items like trim settings, flap and gear handles, and important switches for items like combustion heaters are in the correct position. On simple airplanes this wont be such a big issue but as you move to more complex airframes there are more items that can “bite you” if not caught on the interior inspection.

Hopefully your local FBO or flight school has some sort of system in place to alert pilots when a plane has just come out of maintenance. As a pilot you should be able to review a squawk sheet and see what’s outstanding on the list and what recent repairs have been made. As PIC you should also be checking prior to jumping in that rental to ensure that annual, 100-hour, or 50-hour inspections are current.

As a pilot in the “shared airplane” community not only are you looking for general inoperative or unserviceable items due to normal use but you’re also carefully checking for things other people may have damaged or broken and not realized or not bothered to report.

Individual Owners
My airplanes sit in a fully enclosed and locked hangar I lease from the local airport. Other than my mechanic and the Airport Manager only I have keys to access the hangar. My mechanic doesn’t touch the airplanes unless I ask him to, and if the Airport Manager needs access (such as for the Fire Marshall to conduct his annual inspection) he alerts me in advance or lets me know immediately after. I also keep all cabin and baggage doors locked while in the hangar – something I learned from a friend after thieves stole avionics out of dozens of airplanes in hangars at his airport in the middle of the night.

I can be nearly 100% sure that no one has flown those airplanes or had access to them that I didn’t know about. This makes my preflights a little easier. I still follow the POH/AFM in conducting the inspection but rather than examining each rivet and worrying about hangar rash and hidden damage I am more concerned with finding fuel, oil, or hydraulic leaks that sometime develop with temperature changes or when an airplane sits for awhile.

I also keep a sharp eye out for any evidence of bird, animal, or insect issues. Luckily my hangar is sealed fairly tightly and it’s not something I have had to deal with. I used to own a Piper Arrow that I kept in another hangar. Birds were able to get in and build an entire nest and lay two eggs right on top of my engine in the eight days that passed between flights, so you can never be too careful.

As the sole pilot for a particular aircraft kept in a secure hangar my preflight changes from a search for something another person did to the airplane to items that may break or wear from general usage. On my interior inspection I’m not so worried about the position of trim tabs, autopilot settings, or broken or missing items because I know exactly how everything was left the last time I touched the airplane.

Part 135 or Part 91 Corporate Operations
Here is where things change dramatically as far as preflight inspections go. Depending on the OpSpecs or Operation Specifications a pilot may not even conduct a typical exterior inspection. In our corporate King Air operations originating from our home base an A&P mechanic orders fuel (based on pilot request), supervises fueling, checks tire and fire bottle pressures, samples the fuel, checks the oil levels in both engines, checks battery voltage, ensures all required AD’s and inspections are current, and even typically pulls the airplane out of the hangar for us.

All of this work is documented on a maintenance release form signed by the mechanic and fuel slip provided to one of the two pilots on board. The extent of our exterior inspection upon arrival is usually a quick walk-around looking for major bent, broken, or worn items the mechanic may have missed and ensuring that the maintenance release is completed. We still have a lot of work to do inside the airplane with preflight duties to ensure everything is configured and ready for flight. Between crew and the maintenance staff all required items are completed and this method is perfectly acceptable to the FAA and the operator.

Post-Maintenance Inspections / Aircraft Parked on the Ramp
As I touched on earlier any aircraft just out of maintenance requires extra attention to detail during a preflight inspection. Not just prior to the first post-maintenance flight but quite possibly for the next several flights as well. There have been numerous pilots killed and airframes lost over the years because inspection panels or cowling that was not secured, tools or rags left where they shouldn’t be, or gear or control surfaces that were not properly rigged.

As PIC you should know what work was done on your airplane. If it was a simple oil change extra attention for leaks, loose cowling, or abnormal pressure or temp indications on run-up might be your main focus. If the airplane just came out of an annual inspection every single system on the airplane has been “messed with” and needs careful inspection. In fact the extra attention may not be required just for that first flight, often it will take a few hours in the air or a few cycles to become apparent that certain panels or cowlings were not quite tightened down correctly.

Any airplane that has sat out on the ramp for any length of time and out of view of the pilot or crew should be looked at with added scrutiny. You simply have no way of knowing whether the full tanks you had the night before were drained into the someone else’s gas cans in the middle of the night, a tug clipped the wingtip of the airplane, or a bird’s nest has been undergoing expedited construction inside your engine cowling while you were away.

Although our duties during a preflight inspection may change with experience, aircraft, and circumstances the ultimate goal is to find things that if not repaired may hurt the airplane, passengers, or crew. Sometimes this is a team effort sometimes this responsibility rests solely with the PIC. While not the most exciting part of getting up in the air its one of the easiest to ensure safety of flight.

What are your thoughts on the subject? Do you perform a complete preflight examining every rivet and fastener each time you climb into the airplane or are there circumstances that don’t require such a detailed inspection?

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David Fill – @davidfill – is a Commercial Pilot, Aviation Podcaster, and Aircraft Broker based in the Washington D.C. area.  He flies a King Air for a Part 91 corporate flight department and owns a light twin used for family and personal business transportation.

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