M-20F Flight Instructor and student reported the engine RPMs dropped during initial climb. Pilot was unable to increase RPMs and performed an off field landing.
Synopsis
M-20F Flight Instructor and student reported the engine RPMs dropped during initial climb. Pilot was unable to increase RPMs and performed an off field landing.
Narrative
Weather was checked on ForeFlight before arriving at the airport by checking the METARS; SIGMETS; AIRMETS. Clear weather; no clouds.Aircraft preflight performed 2 times. Once by the instructor (me) before the student arrived and once with the student giving a walkaround on what to look for. Fuel tanks were sumped to check for any contamination (Left; Right and Center near Fuel Swap). Contamination was found on the right tank. The right tank was sumped until contamination was not found anymore. Pre-taxi weather was obtained from ZZZ.Airplane was RUN UP per checklist 1700 RPM mag check normal (Left -30; Right -20); then prop checked at 1900 RPMs there was no drop in RPM during RUNUP (No Oil visible). All checklists were completed including the pre takeoff checklist. Radio calls made before departure. As the aircraft accelerated down the runway engine instruments were in the green. After liftoff at 70 MPH; the aircraft accelerated to 90 MPH. At approx. 150 ft to 250 ft AGL; RPMS started dropping (2300 RPM instead 2600 RPM+). No usable runway and partial climb was available so flaps up and gear up. Then an emergency flow checklist was run which included: Mixture Rich (it was); Fuel Pump Verify on (it was); Mag Check (Left; Right; Both; no effect on RPM increase); Tank swap Left to Right back to Left Tank. (Takeoff was on the left tank).Proceeded to maintain glide airspeed and best landing spot off field because the power wasn't coming back and stall horn was sounding. Landing off field made successfully without any injuries.
Second reporter narrative
All preflight information was checked before the flight.Preflighted the plane multiple times. Once by the instructor before I arrived and once with me receiving instruction while my instructor walked me through how to pre-fight the plane. Sumped all 3 fuel tanks appropriately 15-30 minutes after we fueled up. Water was found in the right tank. The right tank was sumped 3 total times 1 had contamination 2 no contamination 3 verified no contamination.Ranup the plane per checklist 1700 Rpm mag check normal less than 30 on both then Prop checked at 1900 RPM with all checks looking good and a 360 degree turn to verify no oil under the plane. All Checklists were completed including pre takeoff checklist. Radio calls made before departure. Takeoff was made on the left tank since it had no contamination on preflight.On takeoff roll all engine instruments were in the green and had normal performance lifting off well before midfield. The aircraft accelerated to 90 MPH. At approximately 150 feet to 250 feet AGL; RPMS started dropping from the standard 2600+. Because we were out of a usable runway and partial climb was available we configured the plane flaps up and gear up. Returning to the runway was considered; but the RPM continued to decrease until the last option was to maintain best glide speed and max power. A landing site was picked followed by a flow checklist which included Mixture Rich (it was); Fuel Pump Verify on (it was); Mag Check (Left; Right; Both; no effect on RPM increase); Tank swap Left to Right back to Left Tank. None of the following increased RPMs. Off field landing was successfully landed with no persons harmed.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.