A runway is only as good as the soil beneath it; AFCE Structural Assessment team evaluates Wake runway

  • Published
  • By Capt. Amy Hansen
  • 11th Air Force Public Affairs
WAKE ISLAND AIRFIELD --  A two-man team from the Air Force Civil Engineer Support Agency at Tyndall Air Force Base, Fla., visited Wake Island Airfield recently to evaluate the condition and load-carrying capacity of the runways, taxiways, and aircraft parking areas.

Capt. Vincent Bongioanni, Airfield Pavement Evaluation team chief, and Tech. Sgt. Jeremy Morgan, Airfield Pavement Evaluation technician, have traveled to Air Force airfields world-wide to complete their structural testing, and this year Wake was on their list. Air Force airfields do this testing approximately once every 10 years, and Wake's last evaluation was in 1996, according to Captain Bongioanni.

Actually a coral atoll made of three small islands, Wake Island has the longest strategic runway in the Pacific Islands at nearly 10,000 feet, according to Maj. Tammy Dotson, 611th Detachment 1 commander. It is used primarily as a refueling stop and emergency divert field for aircraft transiting the Pacific Ocean, so the integrity of the runway is critical.

The AFCE SA team used visual inspection, destructive testing, and layered elastic modeling to determine the strength of the pavement, according to Captain Bongioanni. The destructive testing consisted of using a special truck to cut 6-inch diameter cylinders from the pavement, called coring. The soil underneath the pavement was tested for strength with an instrument attached to the truck called an automated dynamic core penetrometer.

"It records the number of blows and how deep it goes, and that's part of how we calculate the strength of the runway," said Sergeant Morgan. The coral under the runway was so hard on Wake that Sergeant Morgan said he had to replace the tip of the instrument more than at any other airfield he has tested.

Some of the soil was also sent back to a laboratory at AFCE SA for exact classification. Based on the size of the Wake Island Airfield, over 60 cores were cut and tested over a period of just 3 days due to logistical difficulties getting the specialized truck out to Wake, which is about 2,000 miles from Hawaii.

While the team waited for the trunk, they conducted visual inspections and testing on the surface characteristics of the runway. They measured the slope and texture, and then they used a friction-measuring robot dragged by a truck up and down different sections of the runway at 40 and 60 miles per hour.

The friction measurements relate directly to the potential for an aircraft to hydroplane when the runway is wet, so it is very important for an airfield manager to know this information for safety reasons, according to Captain Bongioanni. He estimated that Wake Island Airfield would not flood until the rainfall exceeded an inch and a half per hour, due to nicely sloped and grooved pavement.

According to the AFCE SA team, when all the on-site and laboratory testing is completed, the data will be processed using a formula called layered elastic modeling. This will result in a Pavement Classification Number, which is a standardized measurement for runways around the world. It will be published in flight manuals so pilots can determine whether they can land on Wake's runway based on the aircraft's weight.

According to Technical Sergeant Morgan, the Air Force and the airfield managers on Wake have nothing to worry about. "The pavement here is ridiculously strong due to the coral underneath. It's great structurally--it's really strong and hard."