NTSB Factual Report

HISTORY OF FLIGHT

On May 30, 2006, at 2043 eastern daylight time, an Embraer EMB-170, N651RW, operated by Shuttle America Corp., as United Express flight 7512, was substantially damaged while landing at the Washington Dulles International Airport (IAD), Dulles, Virginia. The certificated airline transport pilot, certificated commercial pilot, 2 flight attendants, and 56 passengers were not injured. One passenger sustained a serious injury. Visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan was filed for the flight that originated at George Bush Intercontinental/Houston Airport (IAH), Houston, Texas. The scheduled passenger flight was conducted under 14 Code of Federal Regulations Part 121.

According to the flight crew, during initial climbout from IAH, the first officer was unable to raise the landing gear handle to retract the landing gear. The flight crew discussed the situation and did not believe that there was a landing gear malfunction, as they did not observe an Engine Indicating and Crew Alerting System (EICAS) message. The flight crew was unsure which checklist to use in the Quick Reference Handbook (QRH), since the "Gear Lever Cannot Be Moved Up" checklist began with the condition: "LG WOW SYS FAIL message displayed." As they discussed the situation further, they decided that since there was no EICAS message displayed, there was no landing gear problem and the issue must have been with the down-lock. They thought there was no up-lock in the landing gear system, and they would be able to extend the landing gear again. They decided to press the "Downlock Release" button to raise the gear, the landing gear subsequently retracted, and the flight continued to the Dulles area uneventfully.

The flight crew was cleared for a visual approach to runway 19R at IAD, and when the airplane was on the base leg of the traffic pattern, the flight crew performed the "Landing Checklist." While attempting to extend the landing gear, the flight crew received a "LG LEVER DISAG" message on the EICAS, and subsequently initiated a missed approach to troubleshoot the landing gear problem.

The flight crew performed the "Landing Gear Lever Disagree" checklist, which prompted them to the "Abnormal Landing Gear Extension Checklist." They cycled the landing gear several times, during which the cockpit indications were "normal" when the landing gear was retracted, and when the gear was extended, the cockpit indications showed that the main landing gear were extended but the nose landing gear was not.

The flight crew decided to return to the airport, and entered the traffic pattern for a low approach to runway 19L for control tower personnel to visually confirm the landing gear position. Tower personnel reported that the main landing gear were down, and the nose gear doors were open; however, the nose landing gear remained in the wheel well.

The flight crew continued in the traffic pattern while they briefed the flight attendants and passengers of the landing gear problem, and instructed them to prepare for an emergency landing. The flight crew flew an extended traffic pattern for runway 19L, and touched down "normally" on the main landing gear. The Captain held the nose of the airplane up until the airplane "lost elevator effectiveness," and then the nose slowly settled to the runway.

After the airplane came to a stop on the runway, the crew initiated an emergency evacuation using the rear door (2L and 2R) evacuation slides. During the evacuation, one passenger sustained a broken ankle.

PILOT INFORMATION

According to information provided by the operator, the captain held an airline transport pilot certificate, with a rating for airplane multiengine land. The captain reported approximately 6,600 total hours of flight experience, 700 of which were in make and model.

The first officer held a commercial pilot certificate with a rating for airplane multiengine land. The first officer reported approximately 2,800 total hours of flight experience, 1,000 hours of which were in make and model.

AIRCRAFT INFORMATION

According to company records, the accident airplane was manufactured in 2005, and delivered from Embraer to Shuttle America Corp. in May 2005. At the time of the accident, the airplane had accumulated 2,517 total hours of flight time.

On May 27, 2006, the airplane's nose landing gear (NLG) strut was serviced as part of an approved maintenance program. At the time of the servicing, the airplane had accumulated 2,499 hours of operation.

A review of the airplane's maintenance records revealed the following entries during the days preceding the accident:

1) May 28, 2006:

a. Pilot write-up: "Nose strut low, sounds like bottoms out during taxi."

b. Corrective action: "Upon inspection of NLG, found strut extension to be in limits with NLG servicing chart IAW EMB 170 AMM."

2) May 29, 2006:

a. Pilot write-up: "Landing gear did not retract after takeoff. Handle would not move to up position."

b. Corrective action: "Trouble shoot, suspect faulty landing gear handle. Inspected aircraft, found to be safe for ferry flight with landing gear down and pin and safety from ATL to IND."

c. Maintenance write-up: "Aircraft to be ferried from ATL to IND for INOP landing gear handle. Aircraft to be flown with gear down and pin and safety."

d. Corrective action: "Removed and replaced landing gear control lever in accordance with AMM 32-33-01.OP/check good."

A review of the operator's job card, titled "Servicing NLG Shock Strut," dated October 1, 2004, revealed discrepancies when compared to the manufacturer's Aircraft Maintenance Manual (AMM), titled "Nose Landing Gear Shock Strut - Servicing," dated October 20, 2004. The operator's job card did not contain a procedure to fill the shock strut with the final volume of hydraulic fluid.

METEOROLOGICAL INFORMATION

Weather reported at IAD, at 2052, included wind from 150 degrees at 3 knots, 9 miles visibility, scattered clouds at 25,000 feet, temperature 28 degrees Celsius (C), dew point 20 degrees C, and altimeter setting of 30.06 inches of mercury.

FLIGHT RECORDERS

The cockpit voice recorder (CVR) was forwarded to the National Transportation Safety Board Vehicle Recorders Laboratory in Washington, D.C. for analysis.

The two-hour long recording began at 1840, while the airplane was in cruise flight at flight level (FL) 310.

At 1945, after reporting on the Washington Center frequency, the flight crew began discussing the landing gear problem they encountered after departure. The captain stated, "I don't know if the gear not coming up is an emergency but pushing the downlock release would constitute an emergency if we had an EICAS message. I definitely wouldn't have done that." The first officer agreed and stated, "you got two alternate means of lowering the gear...." The first officer also stated that he didn't know enough details about the system to know all the conditions that would keep the lever from coming up.

At 2004, the airplane was cleared to land, the captain called for the landing gear to be lowered, and the first officer lowered the landing gear. Thirteen seconds later, two electronic tones were audible and the first officer stated, "what's up with the gear?" About thirteen seconds after that, the captain called for a go-around and informed the tower of their intentions.

Over the following 15 minutes, the flight crew continued to troubleshoot the landing gear system and performed the abnormal landing gear extension checklist and the partial gear up landing checklist. They declared an emergency and requested a "flyby" for the tower personnel to inspect the landing gear.

During the "flyby" to runway 19L, tower personnel reported to the flight crew that the nose gear door was open but the gear was not down.

The crew then reentered the traffic pattern for runway 19R, and performed a landing on the runway.

TESTS AND RESEARCH

A System's Group was established by the Safety Board, who conducted an examination of the airplane's landing gear system.

The landing gear system was normally operated by manually manipulating the landing gear control lever either up or down. The position of the lever was sensed by micro switches, which were connected to the Proximity Sensor Electronics Modules (PSEM).

The landing gear indication system processed the information coming from the landing gear lock proximity sensors and control lever to provide the landing gear position indication on the EICAS display. The EICAS display of the "LG LEVER DISAG" message indicated that there was a disagreement between the position of the landing gear control lever and at least one landing gear.

The landing gear system also had two alternative modes available to extend the landing gear if necessary; the first mode was provided through an electrical override command, and the second was provided through the free fall emergency release system.

Examination of the cockpit landing gear control panel revealed the override switch remained in the "gear down" position and the mechanical emergency release free fall lever remained in the deployed position.

Using the Central Maintenance Computer (CMC), the landing gear indication system and shock strut position indication system were functionally tested, to determine if an abnormality existed with the NLG proximity sensors. Results of the test revealed no system faults with the landing gear indication system, or the landing gear proximity sensor system.

After completion of the test, the nitrogen was removed from the NLG strut allowing it to compress. The distance of exposed strut ('H') was measured and found to be approximately 23mm. According to the aircraft maintenance manual, the dimension 'H' should be between 76.3 and 78.3mm after hydraulic fluid was serviced and before servicing nitrogen.

On June 1, 2006, the NLG was removed from the airplane and sent to its manufacturer in Brazil for examination, under the oversight of the Brazilian government. Results of that examination revealed the nose gear fluid volume was approximately two-fifths of what a "normally-serviced" gear would contain. No leaks were observed after the nose gear was serviced, the seals were tested, and the gear was cycled. Disassembly of the nose landing gear revealed evidence of "bottoming," or under-service operation.

ADDITIONAL INFORMATION

Aircraft Information

During interviews with the operator and manufacturer, it was determined that an aircraft equipped with the 04 version of the PSEM (earlier version of the hardware), would not generate an EICAS message "LG WOW SYS FAIL" when the nose gear PSEM generated the message "TAKE OFF WOW NLG DISAGREE" to the CMC.

However, aircraft equipped with the 05 version of the PSEM would generate an EICAS message "LG WOW SYS FAIL" when the nose gear PSEM generated the message "TAKE OFF WOW NLG DISAGREE" to the CMC.

The operator had a mixed fleet made of some aircraft equipped with PSEM-04 and some aircraft equipped with PSEM-05. The accident airplane was equipped with PSEM-04 sensors.

Operational Information

A review of the operator's EMB-170 QRH, Emergency and Abnormal Procedures section, revealed that the "Gear Lever Cannot Be Moved Up" checklist read as follows:

"Gear Lever Cannot Be Moved Up

[Condition: LG WOW SYS FAIL message displayed]

1. Landing Gear Lever - DOWN

2. If obstacle clearance is required:

a. Downlock Override - PRESS

b. Gear Lever Cannot Be Moved Up Checklist complete, and

* Accomplish "LG WOW SYS FAIL," page 43.

If obstacle clearance is not required:

a. Gear Lever Cannot Be Moved Up Checklist complete, and

* Accomplish "LG WOW SYS FAIL," page 43."

The same checklist from the Embraer QRH, read as follows:

"Gear Lever Cannot Be Moved Up

Landing Gear Lever - DOWN

LG WOW SYS FAIL Procedure (EAP 13-5) - ACCOMPLISH

NOTE: The downlock override button may be pressed to move the landing gear lever up if climb performance is required to clear obstacles.

If a go-around is required:

Landing Gear - DOWN"

Safety Changes

As a result of the accident, Shuttle America revised their QRH checklist, "Gear Lever Cannot Be Moved Up," to mirror the Embraer checklist. Additionally, Shuttle America also revised their maintenance job card titled "Servicing NLG Shock Strut," to mirror the Embraer AMM for the procedure. Shuttle America also re-serviced all the NLG shock struts that were serviced in accordance with the original maintenance job card.

Also as a result of the accident, Embraer issued an Operations Bulletin, on August 7, 2006, to explain the PSEM differences, and provide guidelines in case the landing gear control lever cannot be moved up.

Embraer also issued a revision of Service Bulletin (SB) 170-32-0019, dated November 12, 2007, which instructed operators to replace PSEM PN 80-003-04 with the newer model, PSEM PN 80-003-05. The revision included information that the "LG WOW SYS FAIL" message would be triggered on the EICAS if any landing gear shock absorber did not fully extend after takeoff, on the -05 models.

NTSB Probable Cause

Improper servicing of the nose landing gear strut and the operator's inadequate maintenance procedure. A factor was the inadequate checklist provided to the flight crew by the operator.