Iran Aseman F100 at Ilaam and Tehran on Mar 22nd 2019, right main gear did not extend, then by luck extended one last time
Last Update: October 19, 2019 / 16:31:07 GMT/Zulu time
Incident Facts
Date of incident
Mar 22, 2019
Classification
Incident
Airline
Iran Aseman Airlines
Aircraft Registration
EP-ATG
Aircraft Type
Fokker 100
ICAO Type Designator
F100
Factors causing the incident, in order of importance, are:
- Faulty design of the landing gear system
- Contamination of the hydraulic system due to negligence of Aseman maintenance personnel
- Insufficient attention to cleanness standards (Part 145) at Aseman maintenance department
- Failure to notice the fault in the system during the preceding flights
The CAO reported that the aircraft had flown 40,110 flight hours in 34,329 cycles before the accident. It had flown 50 hours in 40 cycles in the 12 days before the incident, during which time problems with the landing gear were reported several times. After persisting for 5 consecutive days, the problem was finally solved, only to resurface 5 days later on March 22nd. FDR records from previous flights also indicate that the left and right gears had extension time discrepancies that, if noticed by the crew, would have suggested a problem with the right gear restrictor check valve.
Following the occurrence the aircraft was checked in Aseman’s maintenance hangar where it was observed that the main gear could not be extended in either normal or manual mode. An inspection of the hydraulic system indicated that parts of an O-ring had cut through the screen filter, blocked the restrictor check valve and prevented pressure from being removed off the actuator.
The investigators inspected all lines and modules, from the actuator to the first filter in LG selector valve, in order to find the origin of the dislocated O-ring, but only managed to find other parts of the O-ring. On manufacturer’s request, the O-ring was sent to Netherlands for further inspection. The manufacturer reported that the origin of the O-ring could not be determined, however since the O-ring looked new it was possible that it had entered the system during a maintenance operation. The LG selector valve was also inspected at Aseman where the filter was confirmed to be intact, showing that nothing had entered the system through the reservoir.
It should be noted that the failure of the screen filter had been a longstanding problem on F100 aircraft, and had caused several incidents both in Iran and elsewhere. There had been several modifications to the system and technical directives by Fokker the latest of which happened after this incident when Fokker confirmed design problems, modified the RCV design and issued directives AD2019-0104 and SBF100-32-166R1.
The CAO analysed, that as part of a C Check in October 2018, parts of the system between the selector valve and the actuators had been removed for maintenance. During the procedure and due to negligence, an O-ring had entered the lines. The O-ring then disintegrated within the next few days and moved through the system. The debris was caught in the screen filter, devised to protect the actuator RCV from contamination. However, with time and because of extensive hydraulic pressure (3000 psi) the contamination was pushed into the filter openings, severing the screen and partially blocking the flow. This had caused the disparity between the left and right main gear extension times, but had gone unnoticed by the crew who were preoccupied reading approach and landing checklists. On the day of the incident, the contamination caused a total blocking of the RCV which prevented the removal of hydraulic fluid from behind the actuator. As a result, the gear failed to open.
Incident Facts
Date of incident
Mar 22, 2019
Classification
Incident
Airline
Iran Aseman Airlines
Aircraft Registration
EP-ATG
Aircraft Type
Fokker 100
ICAO Type Designator
F100
This article is published under license from Avherald.com. © of text by Avherald.com.
Article source
You can read 2 more free articles without a subscription.
Subscribe now and continue reading without any limits!
Read unlimited articles and receive our daily update briefing. Gain better insights into what is happening in commercial aviation safety.
Send tip
Support AeroInside by sending a small tip amount.
Related articles
Iran Aseman AT72 near Semirom on Feb 18th 2018, impacted terrain
An Iran Aseman Airlines Avions de Transport Regional ATR-72-212, registration EP-ATS performing flight EP-3704 from Tehran Mehrabad to Yasuj (Iran)…
Iran Aseman F100 at Tehran on Oct 13th 2020, rejected takeoff due to uncontained engine failure
An Iran Aseman Airlines Fokker 100, registration EP-ATE performing flight EP-3962 from Tehran Mehrabad to Ardabil (Iran) with 87 passengers and 7…
Iran Aseman F100 at Ahwaz on May 31st 2020, engine shut down in flight
An Iran Aseman Fokker 100, registration EP-ATF performing flight EP-833 from Ahwaz to Tehran Mehrabad (Iran) with 94 passengers and 7 crew, was…
Iran Aseman F100 at Tehran on May 30th 2020, engine shut down in flight
An Iran Aseman Fokker 100, registration EP-ATF performing flight EP-626 from Tehran Mehrabad to Kermanshah (Iran) with 92 passengers and 7 crew, was…
Iran Aseman AT72 at Tehran on Jun 11th 2018, approach in turbulent conditions, captain refused diversion
An Iran Aseman Airlines Avions de Transport Regional ATR-72-212A, registration EP-ATX performing flight EP-845 from Rasht to Tehran Mehradbad (Iran)…
Newest articles
Dana MD82 at Lagos on Apr 23rd 2024, runway excursion
A Dana Air McDonnell Douglas MD-82, registration 5N-BKI performing flight 9J-352 from Abuja to Lagos (Nigeria) with 83 passengers and 6 crew, landed…
LATAM Brasil A320 at Brasilia on May 13th 2024, engine shut down in flight
A LATAM Brasil Airbus A320-200, registration PR-MYI performing flight LA-3008 from Sao Paulo Congonhas,SP to Brasilia,DF (Brazil) with 106 people on…
Subscribe today
Are you researching aviation incidents? Get access to AeroInside Insights, unlimited read access and receive the daily newsletter.
Pick your plan and subscribePartner
A new way to document and demonstrate airworthiness compliance and aircraft value. Find out more.
ELITE Simulation Solutions is a leading global provider of Flight Simulation Training Devices, IFR training software as well as flight controls and related services. Find out more.
Your regulation partner, specialists in aviation safety and compliance; providing training, auditing, and consultancy services. Find out more.
AeroInside Blog
Popular aircraft
Airbus A320Boeing 737-800
Boeing 737-800 MAX
Popular airlines
American AirlinesUnited
Delta
Air Canada
Lufthansa
British Airways