Mission Report
Mission #05M1288
July 20, 2005
Emergency Locator Beacon Search
Submitted by Capt Kim Kirschman

I received a call from Col Tomlinson at 0015 informing me the Air Force Rescue Coordination Center (AFRCC) was reporting an Emergency Locator Beacon (ELT) signal in the vicinity of the Newton airport.  We discussed aircrew possibilities; I suggested he fly as a crew member to observe the new-style computerized Becker direction finding receiver in use and that a Des Moines squadron member be drafted to complete the aircrew.  Col Tomlinson, Lt Don Wood, and I departed the Ankeny airport at 0119 in N9327E, a Cessna 182R, operating under the call sign of CAP Flight 1327 (CPF1327).  We proceeded eastbound toward the Newton airport at 3500 feet.  Des Moines Approach Control reported that a number of aircraft reported received an ELT signal as far east as Grinnell and as far west as Ames.  At 0127, when we were approximately halfway between Ankeny and Newton, we began to receive an ELT signal on one of the aircraft's standard communications radios.  A few minutes later the direction finding (DF) radio began to receive a signal, displaying very ambiguous readings that by a small margin indicated the signal was coming from our left, or north of our location.  The indications did not seem to stabilize after we flew north for a short time, but the aural signal from the VHF radio was relatively clean so we utilized the wing null method of establishing the probable bearing of the ELT.  (The wing null method is conducted by placing the aircraft in a rather steep bank--typically 45 to 60 degrees--and listening to the signal while making one or more complete circles.  Since the VHF antennae are located above the cabin, the fuselage and wing tend to block the signal when the bottom of the aircraft is most directly 'pointed' toward the ELT, reducing the signal strength delivered to the radio and therefore lowering the audio output in a manner similar to turning down the volume on a car radio.  By noting where the signal strength is lowest during the time the aircraft is turning, it is possible to determine in a rather approximate manner in what direction from the aircraft's present position the ELT might be found.  It should be said the guidance provided by the wing null method is usually quite inexact.)  This process let us to believe the signal was emanating from somewhere to the NNE of our location, so we headed in the direction.

As we proceeded NNE, we made radio contact with CAP610, a ground team from Oskaloosa that was proceeding to the Newton area to support the mission.  The Marshalltown airport was on the general line of our NNE heading, so we viewed that airport as temporary destination and a possible location for the ELT.  As our distance from the airport decreased, the received signal strength increased and the DF radio began to display more stable readings.  When we overflew the airport the DF readings indicated we had passed the source of the ELT signal, so we made a couple of passes over the airport to confirm the ELT's location.  When that was done, we contacted the ground team and instructed them to proceed to the Marshalltown airport.  We then landed on the Marshalltown airport at 0202 and taxied the aircraft past the hangar areas to further confirm the ELT's location.  We were able to conclude the ELT was most likely in a group of T-hangars but we could not further narrow the search.  We therefore shutdown the aircraft and made phone contact with the incident commander, the sheriff's department, the airport manager, and the ground team.

When the airport manager arrived, he began to check hangared aircraft one at a time, looking for blinking lights or other indications that a particular ELT was transmitting.  Since no one present had a portable receiver of any kind, the search was a slow process.  At approximately 0300 the ground team arrived, bringing a portable receiver.  We removed the antenna from the radio to greatly reduce its signal sensitivity, then walked from plane to plane, holding the radio close to the ELT antenna until we found an antenna that was emanating a signal strong enough to result in a very audible signal on the portable receiver.  When the manager disabled that particular ELT, the signal ceased.  The ground team recorded the required information about the airplane and ELT.  The incident commander was notified of the outcome of the mission and everyone went their various ways.  CPF1327 departed Marshalltown at 0336 and landed at Ankeny at 0411, closing the mission for the aircrew.

Total flight time for the mission was 1.6 hours.

Ground team members in Iowa CAP 610: Allen Chilcote, Allen Chilcote II, and Susan Chilcote

Incident Commander: Maj John Halbrook

Lessons of note:

1.    The ELT was located quite a distance from the probable search area as determined by AFRCC and some distance from the area suggested by reports from non-CAP aircraft.  It is very likely the metal hangar housing the offending aircraft and its ELT caused the signal to be radiated in a distorted and misleading pattern.

2.    Cell phone use was a positive factor.  At low altitude and on the ground it was not possible to contact either the incident commander or ground team by using the aircraft CAP radio.  The cell phone made communications quick and easy.  Aircrews and groundcrews should make every effort to have at least one phone aboard, and that phone should be tied to a cell service that provides the widest possible coverage.

3.    Fatigue due to the late hour and abnormal heat could have become a consideration if the search had continued for a lengthy time period.

4.    The Becker DF radio in CPF1327 worked satisfactorily, but it is worth noting that the standard VHF communication radios in the aircraft provided a positive aural indication of the presence of an ELT signal earlier than the DF radio.  Also, even though the Becker is microprocessor driven and is designed and programmed to display the most accurate and stable readings possible about to assist with locating an ELT signal, the radio in fact displayed uncertain indications until within several miles of the ELT.

5.    It would probably be quite useful to equip each search aircraft with a compact and portable DF radio to enable crews to more quickly and efficiently locate ELT signals that are located on airports, especially since a large majority of ELT searches are caused by malfunctioning ELT's housed in aircraft that are firmly on the ground, on an airport, in a hangar.