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N18CC accident description

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Tail numberN18CC
Accident dateDecember 20, 1997
Aircraft typeCady LONG-EZ
LocationWest Milford, NJ
Additional details: None

NTSB description

HISTORY OF FLIGHT

On December 20, 1997, about 1130 eastern standard time, a home-built, Long-EZ, N18CC, was substantially damaged during a forced landing while on approach to land at Greenwood Lake Airport (4N1), West Milford, New Jersey. The certificated private pilot was seriously injured, and the passenger was fatally injured. Visual meteorological conditions prevailed for the personal flight that originated from Farmingdale Airport (FRG), Farmingdale, New York, about 1030. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91.

In the NTSB Pilot/Operator Accident Report, the pilot stated:

"I took off Saturday morning, Dec 20, from FRG for what was meant to be a short round trip to 4N1. Flew north across L.I. Sound and then generally west, avoiding the various NY area controlled airspace's. Visibility greater than 10 mi. from 4N1. Advised traffic on 122.9 (or whatever it was) of our type, location, and intentions. With airport in sight, entered right downwind for Runway 2 at about midfield. This is all clear. But that's where my memory ends...."

An inspector from the Federal Aviation Administration (FAA) reported that witnesses observed the airplane enter a left-hand traffic pattern for Runway 6. When informed on the radio that the pattern for Runway 6 was a right-handed pattern, the airplane crossed over at mid-field, and entered a right downwind for the runway.

A witness who was hiking across the final approach course to Runway 6 reported:

"...with my back to the runway, I heard a loud pop, like a car backfiring, then the engine noise ceased. This happened [when the airplane was] approx. 150 yards from the runway. After the pop, the plane descended, still level until it crashed into the berm in front of the runway. It hit nothing before the hill and where it came to rest was basically the same spot as the impact...."

The accident occurred during the hours of daylight at 41 degrees, 7.55 minutes north latitude, and 74 degrees, 20.72 minutes west longitude.

PERSONNEL INFORMATION

The pilot held a private pilot certificate with an airplane single engine land rating. He was issued a second class FAA Airman Medical Certificate with no limitations on August 13, 1997. According to his pilot logbook, he had accumulated 152 hours of total flight experience, with 37 hours in the accident airplane. He had flown 15 hours in the preceding 90 days, and 6 hours in the preceding 30 days, all in the accident airplane.

AIRCRAFT INFORMATION

The airplane was built from a kit in 1986 and had been issued an experimental airworthiness certificate. It was a canard design with the engine located in the rear of the fuselage. A representative of Scaled Composites, reported the kit originally recommended the use of either a Continental O-200A, or Lycoming O-235 engine. However, a large number of the kit builders in the past few years had installed the Lycoming O-320 engine, including the builder of N18CC. To compensate for the increased engine weight in the rear, and to maintain center of gravity limits within recommended limits, the builder installed a fuel tank with a capacity of 5.5 gallons in the nose of the airplane.

The zero fuel weight and center of gravity for the accident flight, were computed as 1,147 pounds and 103.57 inches. Computations revealed that the addition of 2 gallons of fuel to the nose fuel tank moved the zero fuel weight center of gravity forward to 102.5 inches. With additional fuel added to the wing tanks to the takeoff gross weight of 1,425 pounds, the center of gravity remained forward of the aft limit of 103.0 inches.

The pilot/owner bought the airplane in August 1997. After purchase, he took it to a FAA approved repair station for an annual inspection and any additional required work. Included in the work was an upgrade of the avionics. The two bladed wooden propeller was replaced with a heavier, three bladed wooded propeller. The owner reported that the repair station recommended the addition of higher compression pistons to the engine which increased the engine horse power from 150 to 160. In addition, the right magneto was exchanged for an electronic ignition system, and a noise suppressing headphone system was installed.

METEOROLOGICAL INFORMATION

The pilot reported that he checked the weather prior to departure from his home with a hand held radio tuned to the FRG Airport Terminal Information Service (ATIS), which contained local airport weather including temperature, dewpoint, visibility, cloud cover, etc. A check of the FRG weather reports between 0750, and 1145, revealed the temperature dewpoint spread never exceeded 9 degrees Celsius. A check of weather reports from area airports between 0945 and 1145, revealed the temperature dewpoint spread never exceeded 8 degrees Celsius. The area airports included Avoca, Pennsylvania; Allentown, Pennsylvania; Caldwell, New Jersey and Newark, New Jersey. WRECKAGE AND IMPACT INFORMATION

The airplane impacted the ground prior to, and below the approach end of Runway 6. The terrain sloped up to the end of the runway at an approximate angle of 30 degrees. The airplane came to rest on the lower 1/3 of the slope.

Initial examination of the airplane by inspectors from the FAA revealed that two of three propeller blades were not damaged. Fuel was present in both wing tanks and the main fuel sump. The engine had an MA-4SPA carburetor mounted in place, with fuel in the bowl. The fuel selector was found selected to the left tank. The fuel pump switch was ON. The ignition key was broken off and turned to "R" position.

The nose fuselage tank was broken open. There was no smell of fuel in either the tank or on the ground under the tank. The smell of fuel was present under the wings that were leaking.

The throttle was found in the forward (high power) position, the mixture control was in the forward (full rich) position, and the carburetor heat control was found in the mid-range position between cold and heat.

The air intake inlet for the carburetor heat was found to be pointed opposite to the direction of flight. A representative of Scaled Composites, reported that the design of the engine cowling raised the air pressure in the engine compartment above ambient, and as such, the direction the air intake was pointed was not significant.

The airplane was equipped with a four-light annunciator panel located on the upper 1/3 of the left side of the instrument panel. The bulbs, from left to right were, No Charge, Gear Up, Canopy Open, and Oil Pressure. Filament stretch was found on the filaments of the bulb in the No Charge position.

MEDICAL AND PATHOLOGICAL INFORMATION

A doctor who examined the passenger prior to removal from the airplane reported that the seat belt and shoulder harness were tight.

The Deputy Chief Medical Examiner, State of New Jersey conducted an autopsy of the passenger on December 21, 1997.

TESTS AND RESEARCH

Precision Aeromotive in Everett, Washington examined the carburetor. The FAA Inspector and a representative of Precision Aeromotive who were present for the carburetor examination were interviewed by telephone. They reported that the carburetor was the correct model for both the 150 and 160 horsepower Lycoming O-320 series engines. They also reported that none of discrepancies found on the carburetor examination would be noticeable at an idle or have contributed to a power loss at a low power setting or idle.

ADDITIONAL INFORMATION

The airplane held an experimental airworthiness certificate, and had received a condition inspection (annual) 20 hours prior to the accident.

Griffin Avionics, Inc. accomplished the maintenance work on the engine and avionics in November 1997, at Barnstable Municipal Airport, Hyannis, Massachusetts. They reported the carburetor was equipped with a one piece venturi, and AD#93-18-03 was not applicable. However, the investigation revealed it was equipped with a two piece venturi that was secure.

A maintenance write-up from Griffin Avionics stated:

"ENGINE HARD STARTING ON LEFT MAG - Checked sparkplugs which were found to have some oil on them due to new cylinders. Cleaned and reinstalled. Performed lead breakdown check of ignition leads. Checked good. Removed magneto and opened. Checked all components and internal timing. All checked good. Reassembled and timed to engine. No further action taken."

After the accident, attempts at starting the engine using the left magneto were unsuccessful. When an external electric source was used to power the right side electronic ignition, the engine was started and ran successfully.

In a written statement, the FAA Inspector who conducted the engine run reported, "...Found intermittent spark on high tension leads off of left magneto. Further checking indicated high tension leads leaking through shielding of wire...."

In a follow-up telephone interview, the FAA Inspector explained that he observed spark jumping from the shielding of the ignition harness to ground on the engine. He further added that this is normal for an old or worn harness, and said that the ignition harness visually appeared to be old. He said that this would be more detectable on damp days than dry ones.

The pilot who flew the accident airplane after the engine modification reported:

"...On an early test flight, on the downwind at PVC [Provincetown, Massachusetts, and] with the power at idle, the engine stopped. With the Bose ANR headsets on, my first indication of the stopped engine was when I went to advance the power and got no response. With the throttle lever slightly above idle I turned the key and the engine started immediately. I returned to Hyannis and asked Griffin to adjust the idle stop. On subsequent flights I had the throttle hard at idle both in the air and on the ground and I could not duplicate this situation...."

A check of the carburetor after the accident revealed that the idle stop was tight.

The accident pilot was interviewed in the hospital on December 26, 1997, while he was receiving pain medication for his injuries. The pilot reported that before departure, he checked to make certain the passenger's seat belt and shoulder harness were secure. The flight then departed to the north, across the Long Island Sound, and toward Greenwood Lake Airport. The flight was uneventful until arrival in the traffic pattern at Greenwood Lake Airport. The pilot's memory of the accident events was hazy and he was not sure what had happened. He had no memory as whether or not he had used carburetor heat.

In a follow-up interviews, conducted after the pilot left the hospital, the pilot explained that carburetor heat was not part of his regular landing checklist and had never been, but it was part of his engine out routine. He added that he had learned to fly in airplanes with Lycoming engines, and they were not as susceptible to carburetor icing conditions as other engines. In addition, the landing checklists on the airplanes he flew did not call for the use of carburetor heat as a preventative measure while on approach. He added that he always checked the carburetor heat during the run-up to ensure it was working, and used it in accordance with the flight manuals on the airplanes he flew. When asked what conditions required the use of carburetor heat, he replied flight near or in clouds, or in visible precipitation. He added that on the day of the accident, it was mostly clear, and he was not operating near clouds or in visible precipitation.

The pilot reported that he had designed his own checklist for use in the airplane based upon the previous checklist found in the airplane, the airplane flight manual, and his previous experience with other airplanes that had Lycoming engines. He had listed carburetor heat as a check item on the run-up checklist, but had not listed it on the landing checklist. According to the recommended checklist found in the kit designers flight manual, "CARB HEAT - On as required", was the 4th item on the Descent/Landing checklist.

On page 15, the flight manual stated:

"...Icing can occur during cruise in moist air, particularly at low cruise power settings. When in moist conditions, check carburetor heat often or cruise with heat on...."

The carburetor icing probability chart published by the FAA, placed the temperature/dewpoint as recorded at Caldwell Airport, in the, "SERIOUS ICING AT CRUISE POWER," section.

A check of flight manuals from over 20 airplanes that were equipped with carburetors revealed widely different procedures. Airplanes that were certificated in the 1930s and 1940s were consistent in their recommended use of carburetor heat as an anti-ice preventative procedure, regardless of the type of engine installed. One major airplane manufacturer switched their engine supplier in the late 1960s, but continued to mandate the use of carburetor heat on the same models of airplanes.

The procedures used for the same type of engine in different airframes varied widely. With a Lycoming O-320 engine, one major manufacturer stated, "ON (apply full heat before closing throttle)", and on a later model stated, "FULL HEAT AS REQUIRED (to prevent carburetor icing)". Another major manufacturer using the same engine stated, "OFF (unless icing conditions exist)", and on another model dropped all reference to carburetor heat in the APPROACH AND LANDING checklist; however, they did state in the flight manual:

"...Carburetor heat should not be applied unless there is an indication of carburetor icing, since the use of carburetor heat causes a reduction in power which may be critical in case of a go-around. Full throttle operation with carburetor heat on is likely to cause detonation...."

FAA guidelines for carbureted engines required the installation of carburetor heat in certificated airplanes, but did not required a procedure for its use. Procedures for use of carburetor heat were determined by the airframe manufacturers. There was no requirement for an airframe manufacturer to follow the carburetor heat procedures contained in the engine manufacturers manual. The investigation revealed that in some instances, the airframe manufacturers procedures differed from the engine manufacturers procedures.

On October 22, 1981, the FAA published Advisory Circular 20-113 PILOT PRECAUTIONS AND PROCEDURES TO BE TAKEN IN PREVENTING AIRCRAFT RECIPROCATING ENIGNE INDUCTION SYSTEM AND FUEL SYSTEM ICING PROBLEMS. This detailed various types of carburetor ice and stated:

"...It is usually preferable to use carburetor heat or alternate air as an ice prevention means, rather than as a deicer, because fast forming ice which is not immediately recognized by the pilot may significantly lower the amount of heat available from the carburetor heating system...In general, when the temperature/dewpoint spread reaches 20 degrees F. [11 degrees Celsius] or less, you have a relative humidity of 50 percent or higher and are in potential icing conditions."

The accident pilot reported that he was aware of the increased hazards associated with higher relative humidity. However, he was unaware of how to determine if the relative humidity was greater than 50 percent, and about the significance of 50 percent relative humidity in relation to the formation of carburetor ice. A check of several general aviation pilots including flight instructors found that over half were not aware of the relationship between temperature/dewpoint spread, and relative humidity, and the significance of 50 percent relative humidity as it relates to carburetor icing probability.

Two questions on the private pilot examination covered the temperature range where there was an increased probability of carburetor ice. Neither question covered the significance of 50 percent relative humidity, or how to compute relative humidity. None of the eight questions related to the use of carburetor heat as a preventative measure with reduced power.

None of the airplane handbooks, owners manuals, or FAA approved airplane flight manuals that were examined contained any information on the dete

(c) 2009-2011 Lee C. Baker. For informational purposes only.