What’s up with unpaved field certification?

In August 2024, Piper Aircraft announced the M700 Fury’s certification for unpaved field operations. My first thought? What’s that about?

As if reading my mind, commenter Are Cee wrote, “So, what is involved in ‘upaved field’ certification? Is that an actual certification, as in without it you’re illegal to land on, say, Triple Tree? Or is it a marketing gimmick? Not being snarky, I am truly curious.”

Here’s the short version:

• What’s involved? Quite a bit. Keep reading.
• Actual certification? Yes.
• Marketing gimmick? No. But it does let manufacturers highlight the aircraft’s added utility.

Unpaved Field Certification

Unpaved field certification ensures an airplane — regardless of its weight or landing gear — can safely operate on surfaces beyond standard paved runways. The certification process evaluates performance, safety, and durability on more challenging surfaces.

Since Piper’s M700 Fury sparked the question, I called Piper and spoke with Joel Glunt, Manager of Engineering Flight Test. He pointed me to FAA Advisory Circular (AC) 23-8C, Flight Test Guide for Certification of Part 23 Airplanes.

The M700 has narrow, high-pressure tires. Maximizing the utility of the airplane required Piper engineers to test it on a variety of unpaved surfaces.

The M700 is approved for hard dirt and dry grass runways, though grass height has limits.

Wet grass? Not approved.

Gravel? Also a no, mainly due to propeller clearance issues.

FAA Guidelines

AC 23-8C spells out unpaved runway requirements, as well as ground handling characteristics.

Section 2 — Performance — is where unpaved runway operations (23.45.c) is discussed.

For aircraft under 6,000 pounds, manufacturers have the option of using values with conservative multipliers to adjust performance data:

Table 4: Smooth, Flat Runway

For example, wet grass adds 60% to your ground roll distance.

Cirrus’s SR22 Pilot’s Operating Handbook (POH) gives similar guidance: “Dry Grass Runway — Add 40% of ground roll to table distances.”

Cub Crafters CC18-180 POH simply states, “The CC-18-180 may be operated from paved and unpaved runways.”

Heavier aircraft (6,000 pounds and above) require FAA approval and performance data for each unpaved surface. This includes defining surfaces, verifying the airplane’s safety during operations, and determining special procedures.

Generic to all Part 23 aircraft, Section 9 — Ground and Water Handling Characteristics — states, “Landplanes should be operated from all types of runways applicable to the type of airplane. Taxi, takeoff, and landing operations should be evaluated for acceptable characteristics.”

As you might imagine, the regulations (23.235) require the shock-absorbing system to operate as intended and the airplane must be tested on the worst/roughest runways appropriate for the airplane.

And the regulations state that those tests should produce “no evidence of damage to the airplane during these operations.”

The more I read through this, the more it made sense.

It is similar to comparing an airplane taking off from a sea level airport to taking off from Lake Country Airport (KLXV), in Leadville, Colorado, elevation 9,934 feet. Same plane, different environment. Test the options and report the performance.

If you land on an unpaved runway in an airplane without an approval for operating on that runway type, and something goes wrong, I’d expect your insurer to scrutinize that event closely.

Thanks for asking Are Cee.