Date: 201505
Local time of day: 1801-2400
Location: MMMX.Airport, FO
Flight conditions: IMC
Weather elements / visibility: Icing
Light: Daylight
Aircraft: Light Transport; Low Wing; 2 Turbojet Eng
Operator: Air Taxi
Operating under: Part 91
Flight plan: IFR
Mission: Ferry / Re-Positioning
Flight phase: Cruise
ATC / advisory: Center MMEX
Aircraft component: Landing Gear
Reporter organization: Air Taxi
Reporter function: Pilot Flying; First Officer
Second reporter function: Pilot Flying; Captain
Anomaly: Deviation - Speed All Types; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Contributing factors: Weather; Environment - Non Weather Related; Aircraft
Primary problem: Weather

Narrative: Approximately 20 minutes into our Ferry Flight with the landing gear extended; we encountered icing conditions picking up light to moderate rime ice; while at FL200.  As we were already flying slowly; at approximately 200 IAS; my Captain and I discussed our options.  The MEA was 20;000 feet; and our limitation with gear down was also 20;000 feet.  We decided to call center to see if they could give us vectors off airway to a lower altitude since our indicated airspeed was degrading.  ATC gave us a vector off airway and a lower altitude of FL180; to which I started descending immediately to increase airspeed as well as get out of the icing conditions.  This worked; within a few moments we were out of the icing conditions and our airspeed returned.  No further incidents; we landed safely at our destination airport.We were VFR at the departure airport and arrival airport; and there was no en-route weather forecast on our flight release.  We could not have raised landing gear in this circumstance as they were braced with gear locks in the down position for maintenance so they could be inspected upon return to the USA. While we were VFR at our departure airport; and arrival airport; our level of safety would have been greater had the routing also been forecast as VFR.


Second narrative: We encountered icing conditions on maintenance ferry flight. Landing gear extended V(LE) 220 kts and FL200 and above max altitude. Airspeed slowed to 190 kts with rime ice build up; engines at maximum power allowed with engine and airfoil heat on. Minimum Obstruction Clearance Altitude for airway was FL200. Captain contacted [ATC] requesting a lower altitude. The decision was made to depart the airway; allowing descent to FL180. Airspeed continued to bleed off to 170 kts; when ice began to break off. After 15 minutes the aircraft was clear of clouds and return to normal flight at 210 kts; with engine and airfoil heat off was possible. Icing was not forecast when weather brief received. Landing gear was locked down; preventing retraction and the option of increasing airspeed and altitude.A. Do not conduct landing gear down ferry flights in mountainous terrain when clouds are present.B. Gear down ferry flights should only be conducted in VMC conditions.C. Do not depart 'the Black Line' unless under positive ATC radar controller contact.D. Do not lock gear down as it severely limits the pilot's options.


Synopsis: A flight crew on a gear down ferry flight at FL200 encounters icing conditions and begins to lose airspeed with max power set. Flight level 200 is the maximum allowable altitude with the gear extended and the MEA for the airway. A vector off the airway allows a descent to FL180 where the ice melts and airspeed is regained.