Engine failures are bad enough. But how about attempting a takeoff with one engine inoperative? You can probably imagine how this one ends...
NTSB Report: One Terrible Takeoff Plan
In 1998, an Aerospatiale SN-601 Corvette, N600RA, experienced a loss of control during an attempted takeoff from Runway 10L at Portland International Airport, KPDX. The aircraft impacted signs, lights, and terrain on the airport property, sliding upright for approximately 1/2 mile following initial ground contact and came to rest on airport property southeast of the runway 10L departure end. The airplane was totaled.
The commercially rated pilot and three passengers escaped the aircraft without injury, which was shocking considering they had attempted a single-engine takeoff in a twin-engine jet. Here's the NTSB report:
The flight originally received an instrument flight rules (IFR) clearance to Hermiston, Oregon. After taxiing out from the parking ramp at a fixed-base operator (FBO), the pilot called Portland ground control and stated he wanted to return to the ramp.
Witnesses at the FBO reported that after returning to the, the airplane shut down and opened its main entry door, and that one of the aircraft occupants told ground service personnel the aircraft had an engine problem. The aircraft remained there for approximately 5 minutes, then started back up and taxied back out. After taxiing out the second time, the pilot cancelled his IFR flight plan to Hermiston with ATC, and requested and received a VFR clearance to Redmond, where the accident aircraft was based.
The cockpit voice recorder (CVR) recording indicated that the pilot was unable to start the right engine before takeoff, and elected to attempt takeoff with the right engine inoperative. Witnesses reported that the airplane's nose lifted off about 4,100 feet down the runway and that it then became airborne with its wings rocking, attaining a maximum altitude of 5 to 10 feet above the ground before settling back to the ground.
Investigators removed the right engine starter-generator from the engine after the accident and found the starter-generator drive shaft to be fractured. The aircraft has a minimum crew requirement of two, consisting of pilot and copilot; the copilot's seat occupant, a private pilot-rated passenger, did not hold a multiengine rating and thus was not qualified to act as second-in-command of the aircraft.
This Goes Without Saying...
Ok, so you may be thinking to yourself WELL DUH...of course they crashed. And you're right. But let's dig into a few reasons why taking off single-engine in a twin-engine airplane is such a bad idea.
One-Engine-Inoperative Takeoff Obstacle Clearance Requirements
Chapter 1 of the Instrument Procedures Handbook discusses one-engine-inoperative (OEI) performance requirements in great detail. And while this pilot attempted to depart under VFR, the same performance losses obviously apply.
Simply put, there is no performance data for the takeoff roll during a single-engine takeoff in a twin.
Even if they had made it off the ground, the performance loss would've been a big problem too. The FAA requires that turbine-powered, multi-engine transport category airplanes and commuter category airplanes operated under Part 121 or Part 135 have additional takeoff obstacle clearance requirements beyond the scope of the IFR departure procedure requirements addressed by TERPS. Performing a single-engine climb truly is an emergency situation.
Minimum Control Speed: Vmcg
Vmcg is the minimum speed, while on the ground, that directional control can be maintained using only aerodynamic controls with one engine inoperative. As airspeed increases during takeoff, your control surfaces interact with airflow to create aerodynamic forces. During an engine failure, additional propulsion from the operating engine creates asymmetric thrust, resulting in a strong yawing moment towards the dead engine.
When your aerodynamic control inputs are no longer able to counter this asymmetrical thrust created with one engine failed, you've reached Vmcg and the airplane is no longer controllable. Only aerodynamic controls are used during Vmcg determination, as nose wheel steering and differential braking may have no effect on a wet or icy runway.
Vmcg for the Cessna Citation CJ3 series, and aircraft similar in size to the SN-601 Corvette, is about 95 knots at maximum takeoff thrust. With rotation speeds 10-20 knots faster than this depending on weight, you'll reach Vmcg well before liftoff in a CJ3.
Minimum Control Speed: Vmca
Vmca is the minimum speed, while in the air, that directional control can be maintained with one engine inoperative (critical engine when applicable), with the operating engine(s) at takeoff power and a maximum of 5 degrees of bank towards the good engine(s). Just like Vmcg, the asymmetrical thrust created by the operating engine will require significant control inputs for level flight.
Vmca is the speed at which your control inputs can no longer oppose asymmetric thrust. In this case, the accident aircraft lifted off by 5-10 feet shortly before crashing. It's likely that once they left ground effect, airspeed below Vmca led to the crash.
What Do You Think?
Like us, you're probably wondering "what were they thinking?" There's too much to unpack in this report for one article. That being said, external pressures, and the desire to get back to their home airport, led to some very poor decision making.
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