The scenario
In the final seconds of the Tu-154M flight over Smolensk North airfield on April 10, 2010, the aircraft was in the following configuration:
- Mass: approx. 76,000 kg
- Flaps: 36° (landing configuration)
- Landing gear: deployed
- Forward velocity: ~270 km/h (~75 m/s)
- Vertical descent speed: ~7 m/s
- Thrust: engines at idle (~40 kN total), beginning to spool up
- Time required to reach full take-off thrust: ~8.5 seconds (per D-30KU-154 engine specs)
In such a situation, pilots may instinctively try to pull back and raise the nose, increasing the angle of attack (AoA) to stop the descent.
This intuitive reaction is aerodynamically dangerous under these conditions, and can quickly lead to stall and loss of control.
Why increasing angle of attack without sufficient thrust is dangerous
Drag increases dramatically:
As AoA increases, induced drag rises non-linearly with the square of lift coefficient (CLC_LCL),
The aircraft demands even more thrust, which it does not have at that point.
Approaching the critical AoA — stall risk:
Beyond ~16–18°, airflow separates from the wing’s upper surface,
Lift collapses, and the aircraft may enter a deep aerodynamic stall.
Loss of pitch control:
In deep stall, elevator effectiveness is reduced,
Tu-154M has a T-tail configuration, increasing the risk of „deep stall”, where the horizontal stabilizer is immersed in turbulent wake behind stalled wings.
Post-stall trajectory is ballistic:
The aircraft becomes nearly uncontrollable in pitch,continues on a steep descending arc with no meaningful aerodynamic recovery unless large altitude and thrust margins are available — which they weren’t.
Continues on a steep descending arc with no meaningful aerodynamic recovery unless large altitude and thrust margins are available — which they weren’t.
The 2010 Moscow simulator experiment: unrealistic success?
In July 2010, the Interstate Aviation Committee (MAK) conducted a go-around simulation on a full-flight Tu-154M simulator in Moscow. Their reported results showed:
Aircraft successfully transitioned into a climb.
Sink rate arrested within 19–23 meters,
Maximum load factor: up to 1.5 g,
But serious doubts exist about the realism of this simulation:
1. Thrust ramp-up may have been artificially accelerated:
- Real D-30KU-154 engines require ~8.5 seconds from idle to take-off thrust,
- The simulator may have implemented idealized (faster) thrust response for testing purposes.
2. Load factors in the simulation exceeded those recorded in the actual flight:
- Flight data recorder (FDR) from Smolensk flight: max 1.35 g,
- Simulator run: 1.5 g, suggesting aggressive pitch-up or unrealistic flight envelope margins.
3. In the simulation, flaps were retracted or repositioned (e.g., 36° → 28°):
Without this change, drag remains too high for successful climb-out.
In the real flight, no such configuration change occurred — no command, no attempt.
Conclusion for investigators and analysts
- Increasing the angle of attack under low thrust and high drag conditions does not stop descent — it accelerates stall,
- In Tu-154M, this leads to rapid loss of lift and control, especially with gear/flaps extended,
- The 2010 Moscow simulation, although technically interesting, used flight parameters not observed in the real Smolensk flight.
Therefore, its conclusions — particularly the minimal sink rate of 19–23 meters — cannot be considered physically representative of what was possible in the actual aircraft’s state.
Summary:
- The combination of low initial thrust, landing configuration, and attempting to pitch up aggressively would have pushed the Tu-154M into a deep stall, not into a climb.
- Realistic simulation shows minimum altitude loss of ~100 meters, unless flaps were retracted and full thrust already available.
- Any attempt to claim otherwise must justify how thrust, drag, load factors and configuration handling in the simulator reflect actual aircraft limitations — which is highly questionable.
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