Accelerated Stalls

A stall that occurs any time the G-load exceeds +1G — turning, pulling up, or any abrupt change in flightpath (AFH 5-19). It is called an accelerated maneuver stall because the load factor, not the airspeed, got the airplane there.

The sentence to give the student: the wing always stalls at the same AOA, but at a higher load factor it reaches that AOA at a higher airspeed. The rest of the maneuver follows from that one line.

Stall speed increases in proportion to the square root of the load factor (AC 61-67C, par. 100g).

• At 2G, stall speed is up about 41 percent — the AFH's example is a coordinated, level 60° banked turn, which is 2G and stalls 41 percent higher than the 1G speed (AFH 5-9).
• At 4G, an airplane with a 45-knot 1G stall speed can be stalled at 90 knots (AC 61-67C, par. 100g).

Know the published stall speed for 45° of bank, flaps up, before you fly the maneuver — it is typically in the AFM (AFH 5-19).

• Entry altitude allowing completion no lower than 3,000 feet AGL — double the power-off/power-on floor (AI.X.E.S2).
• Configuration as specified by the evaluator (AI.X.E.S3).
• Power set so the airspeed does not exceed VA — or any other POH/AFM limitation (AI.X.E.S4).
• A coordinated 45° bank, increasing elevator back pressure smoothly and firmly until the impending stall (AI.X.E.S5).

The AFH adds one prohibition the ACS assumes: never practice accelerated stalls with the wing flaps extended, because of the lower design G-load limitations in that configuration (AFH 5-19).

VA is the maximum speed at which the positive design load limit can be imposed either by a gust or by full one-sided deflection of one control surface without structural damage (AFH 5-19).

The chain of reasoning:

• At or below VA, pulling to the critical AOA unloads the wing before the design load limit is reached. The stall is the structural protection (AFH 5-19).
• Above VA, the airplane can reach its design load limit at less than the critical AOA — you can bend it before it stalls, and if you keep pulling you add load with no aerodynamic relief (AFH 5-19).
• VA falls with weight. A lighter airplane accelerates more for the same input: "Maneuvering speed is lower at a lower weight" (AC 61-67C, par. 100l).
• VA is not a blanket permission. Rapid, large alternating control inputs — especially combined with large pitch, roll, or yaw excursions — may result in structural failure at any speed, even below VA (AC 61-67C, par. 100f).

VO is the historical operating maneuvering speed applicable to certain airplanes: the maximum speed where, at a given weight, full control excursion may be applied without exceeding the design limit load factor (AFH 5-19).

Method 1 — the common one. From straight-and-level at an airspeed at or below VA/VO, roll into a coordinated, level-flight 45° turn, then smoothly, firmly, and progressively increase AOA with back elevator until the stall.

Method 2. Roll into a coordinated, level 45° turn at an airspeed above VA/VO. After the airspeed slows to VA/VO — and at an airspeed 5 to 10 percent faster than the unaccelerated stall speed — progressively increase AOA until the stall.

Either way, expect the increased back pressure to increase lift and G load, push you down in the seat, and increase drag, which may cause the airspeed to decrease.

In a coordinated turn the airplane stalls much as it does wings-level — the nose pitches away from the pilot because both wings stall nearly simultaneously — except that the stall buffet can be sharper (AFH 5-20).

If it is not coordinated at the stall, the behavior may include a change in bank angle until the AOA has been reduced (AFH 5-20).

Why it surprises people: stalls from abrupt maneuvers tend to be more aggressive than unaccelerated +1G stalls, and they occur at higher-than-normal airspeeds or at lower-than-anticipated pitch attitudes (AFH 5-20). The sight picture the student learned in power-off stalls is simply absent.

Follow the POH/AFM recovery procedure (AI.X.E.S7). Generically (AFH 5-20):

1. Apply forward elevator pressure as required to reduce AOA and eliminate the stall warning.
2. Level the wings with ailerons, coordinated with rudder.
3. Adjust power as necessary.
4. Configure per the manufacturer, accelerate to VX or VY (AI.X.E.S8).
5. Return to the assigned altitude, heading, and airspeed (AI.X.E.S9).

Cost of delay: because an accelerated stall may put the airplane in an unexpected attitude, failure to execute an immediate recovery may result in a spin or other departure from controlled flight (AFH 5-20).

The AFH names four scenarios (5-19):

• Improperly executed turns
• Stall and spin recoveries
• Pullouts from steep dives
• Overshooting a base-to-final turn

The base-to-final one is the killer and it's worth linking explicitly to Task X.F. AC 61-67C adds the mechanism (par. 100g): if the nose falls during a steep turn and the pilot raises it without shallowing the bank, the turn tightens and can lead to a diving spiral. If the aircraft exceeds maneuvering speed, structural damage may result before it stalls.

Two more from the same paragraph: a stall entered from straight-and-level or from an unaccelerated straight climb produces no additional load factor — which is precisely why the accelerated stall must be taught separately.

• 3,000 feet AGL floor — the highest of the standard stall tasks, because the recovery can involve an unexpected attitude and a spin is a live possibility (AI.X.E.S2).
• Verify VA for today's weight before you fly, not from memory. Lower weight, lower VA.
• Flaps up. No exceptions (AFH 5-19).
• Watch the ball into the break. An uncoordinated accelerated stall is a spin entry with extra energy — the risk list names secondary stalls, cross-control stalls, and spins together (AI.X.E.R5).
• Watch the G on the pull-out. Recovery from a nose-low attitude at speed can load the airplane hard; AC 61-67C warns that significant load factor increases are sometimes induced during pull-up after recovery from a stall or spin (par. 100g).
• Collision hazards (AI.X.E.R7). Clear the area — it is a graded skill element, not a courtesy (AI.X.E.S1). This Task deserves more of it than the others: you enter from a 45° banked turn, so the raised wing masks an entire quadrant, the nose comes up through the horizon at the break, and the recovery can end nose-low and fast in an unexpected direction. Do clearing turns in both directions, look above and below the practice block, and assign the student a specific sector to scan and call. Keep the practice area away from published routes and away from other training aircraft working the same altitude band — everyone practices stalls at the same round numbers.
• Take the controls if the bank steepens uncommanded past roughly 60°, if rotation starts, or if the airspeed is building nose-low — at that point you are managing a spiral, not a stall.

The objectives, verbatim from the AFH (5-18): determine the stall characteristics of the airplane, experience stalls at speeds greater than the +1G stall speed, and develop the ability to instinctively recover at the onset of such stalls.

Brief in this order, following the anxiety-management sequence (AIH 2-12):

1. The aerodynamics — same AOA, higher speed, square root of load factor.
2. The number — compute today's 45°-bank stall speed and say it out loud, so the airspeed indicator confirms rather than surprises.
3. The sensations — G pushing them into the seat, a sharper buffet, possibly a bank change, a nose that pitches away faster than they expect.
4. The recovery — unload first, then wings level, then power.
5. The limits — VA for today's weight, flaps up, and the altitude floor.

Then demonstrate it, then let them fly it. Explanation, demonstration, learner performance, supervision, evaluation (AIH 5-21).

"Unload, then roll" — that's the correction. Name the physics, not just the error: rolling level while still at critical AOA does nothing to unstall the wing, and the down-going aileron increases that wing's AOA and induced drag, which can deepen the stall and roll the airplane further (AFH 5-15). At 45° of bank and elevated G, that's how a training stall becomes a spin entry.

The AFH lists it as a discrete common error — "Pilot attempts to level the wings before reducing AOA" (AFH 5-21) — and gives the reasoning: reducing AOA first is what orients the lift vector properly for an effective recovery, and both roll stability and roll control improve considerably after getting the wings flying again (AFH 5-16).

Three reasons you should be able to articulate:

1. The entry is at higher energy. Stalls that result from abrupt maneuvers tend to be more aggressive than 1G stalls (AFH 5-20).
2. The recovery can start from an unexpected attitude, and failure to recover immediately may result in a spin or other departure from controlled flight (AFH 5-20).
3. The pull-out costs altitude. Recovery involves a tradeoff between loss of altitude (and an increase in airspeed) and an increase in load factor in the pull-up (AC 61-67C, par. 100g) — you either use altitude or you use G.

So the ACS sets 3,000 feet AGL (AI.X.E.S2), matching the demonstration stalls in Tasks F, G, and H rather than the 1,500-foot floor of C and D.

An accelerated stall is a stall — the wing has exceeded critical AOA and the fix is to unload.

A spiral dive is a nose-low upset in which the airplane is not stalled: it is flying very tight circles in a nearly vertical attitude and is accelerating, with airspeed and G-load increasing rapidly (AFH 5-27). AC 61-67C describes the spiral mode as an autorotation mode similar to a spin, but with the airplane not stalled, and warns that side forces build very rapidly and recovery must be effected immediately before exceeding structural limits (par. 112).

The discriminator to teach: watch the airspeed. Increasing airspeed means you are not stalled — you are spiraling. The spiral recovery is to release back pressure, neutralize the rudder, and recover from the steep dive, avoiding abrupt or excessive elevator inputs that could produce a secondary stall (AC 61-67C, par. 112). Reducing power to idle first slows the acceleration (AFH 5-27).

Pulling on a spiral dive as if it were a stall is how airplanes come apart in flight.