TODAY'S AIRPLANE
Moves true airspeed and the pitch estimate only — every KIAS number stays put.
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TODAY'S NUMBERS
30° STALL
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KIAS · POH p. 5-17, scaled
BAND AT THE 90
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5–10 above stall · AFH p. 10-7
AT THE 45
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halfway check · technique
VO
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POH p. 3-8
PITCH AT THE 45
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first try · estimate
KNEEBOARD LINE
CHECKRIDE DAY — FIVE STEPS
- Work out today's numbers before the flight. Weight changes them; altitude doesn't.
- Use the 45 as your early check. About halfway between entry and target. Faster → add a little nose. Slower → ease off before the speed runs out at the 90. technique
- Set power at entry and leave it. Use the setting that holds 120 level at the entry altitude. Power and bank decide altitude at the 180 (AFH p. 10-7).
- Use the first 180 to correct the second. Read the airspeed at the first 90 — the FLY tab works out the change. technique
- Calibrate before the ride. Log the pitch at the 45 that gave the band and the power that held 120 (PITCH tab).
BAND AT THE 90
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brief horn at the 90
AT THE 45
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halfway check
SPEED YOU SAW AT THE 45
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SPEED YOU SAW AT THE 90 → NEXT CLIMBING TURN
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AT THE 180
High at the 180a little power off
Low at the 180a little power on
45 came before the nose was highestroll in slower
AFH p. 10-7 — power and bank decide altitude gained or lost; a slow, even rate of roll.
VS =
69 KCAS
THE BOOK'S
wings level · 3,150 lb · p. 5-17
×
√n
THE BANK'S
n = 1 ÷ cos bank
×
√(W ÷ 3,150)
YOURS — THE LOAD
lighter wing, lower stall
+
≈2 kt
THE GAUGE'S
KCAS → KIAS, POH rows
AFH p. 10-7 and ACS S5a: about 30°. Half of it at the 45 and the 135.
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Show the math
POH STALL SPEEDS AT THIS WEIGHT · flaps 0% · KIAS · tap a bank to fly it at the 90
0°
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TODAY'S AIR · same KIAS, more KTAS ·
STALL AT THE 90
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BAND · LOW
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BAND · HIGH
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ENTRY
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TRY THIS
1 · A light-day number in a heavy airplane. 2,300 lb, slowest 72 (on target). Then tap “1 · then 3,150 lb” — the wing stalls before the 90.
2 · A heavy-day number in a light airplane. 2,300 lb, slowest 83.5 (the 3,150-lb band) — above the band: not enough pitch-up.
3 · Bank at the top. Tap 45° on the stall row: the stall at the 90 jumps about 7 kt at every weight.
4 · Altitude. Slide density altitude from 0 to 10,000 — the speed chart doesn't move; only true airspeed climbs.
2 · A heavy-day number in a light airplane. 2,300 lb, slowest 83.5 (the 3,150-lb band) — above the band: not enough pitch-up.
3 · Bank at the top. Tap 45° on the stall row: the stall at the 90 jumps about 7 kt at every weight.
4 · Altitude. Slide density altitude from 0 to 10,000 — the speed chart doesn't move; only true airspeed climbs.
PITCH AT THE 45 — A FIRST TRY derived · not published
Show the math
No FAA or Cirrus source gives a pitch number for lazy eights — the AFH grades where things happen (highest pitch at the 45, slowest at the 90); the ACS grades speed, bank, altitude and heading. This is my own physics: the speed you give up becomes climb; spread over the first 90 that gives a climb angle at the 45; add the nose-up the airplane already holds in level flight. Speed alone — power adds a little more climb, so a little more pitch.
MY CALIBRATED NUMBERS
From practice flights. Your numbers beat the estimate. Saved on this device only.
Why the POH prints one weight — and how to get the rest
The stall table on p. 5-17 is for 3,150 lb only. A lighter airplane needs less lift, so the wing reaches its stalling angle of attack at a lower speed.
Lift grows with speed squared, so the stall speed comes down with the square root of the weight — the lift equation (PHAK Ch. 5). That step is derived; it is not a POH number.
The scaling is done on the calibrated speed (KCAS). The airspeed indicator's error near the stall is then added back from the same POH rows (71 KIAS = 69 KCAS wings level).
Altitude — same indicated stall, more true airspeed
The wing stalls at the same critical angle of attack at any density altitude (PHAK Ch. 5). Lift depends on how hard the air pushes on the wing — density × speed². The pitot tube measures that same push, density included.
In thin air it takes more true airspeed to make the same push, and the airspeed indicator reads the push, so the stall shows the same KIAS. That's why the POH stall table has a weight and a bank column but no altitude column.
What altitude does change: the stall, the band and the entry all happen at a higher true airspeed, so more groundspeed. VO is indicated too, so the VO check doesn't change with altitude.
Fine print: at very high altitudes, compressibility starts to raise the indicated stall. That's for jets in the flight levels, not an SR20 below 17,500 ft. Not modeled.
Fine print: at very high altitudes, compressibility starts to raise the indicated stall. That's for jets in the flight levels, not an SR20 below 17,500 ft. Not modeled.
Where this stall line is cautious
The POH stall speeds are power idle, in a level, coordinated turn (n = 1 ÷ cos bank). A lazy eight is flown with power on. Over the top the nose is passing down through level, so the wing carries a little less than a level turn's load.
Both put the real stall a little lower. How much lower isn't published, so the app uses the POH line as the cautious edge and puts the 5–10 kt band above it.
CG: at flaps 0% the POH's most-forward and most-aft CG rows are the same (p. 5-17), so CG doesn't move these numbers. It does at flaps 50% and 100%.
CG: at flaps 0% the POH's most-forward and most-aft CG rows are the same (p. 5-17), so CG doesn't move these numbers. It does at flaps 50% and 100%.
Sources and what's derived
FAA / POH: POH/AFM P/N 11934-005 — stall speeds p. 5-17 (3,150 lb only · flaps 0% 71/72/76/83/98 KIAS = 69/70/74/82/98 KCAS at 0/15/30/45/60° · power idle · most-forward and most-aft CG rows identical at flaps 0%); VO p. 3-8 (133 / 123 / 114 KIAS at 3,150 / 2,700 / 2,300 lb, straight-line between).
AFH FAA-H-8083-3C pp. 10-6–10-7, Fig. 10-4: 45° point max pitch-up, bank ≈15° · 90° point bank ≈30°, minimum speed about 5 to 10 kt above stall, pitch through level · 135° point max pitch-down · 180° point level, entry airspeed and altitude · entry at maneuvering or cruise speed, whichever is less, or the manufacturer's speed. AFH p. 10-2: as the load factor increases, so does the stalling speed. ACS AI.IX.D S5a ≈30° at the 90. Cirrus iFOM Lazy Eights: 120 KIAS entry, 2,000 ft AGL minimum. PHAK Ch. 5: an airplane stalls at the same critical angle of attack regardless of airspeed, weight, load factor or density altitude.
Derived (labeled): stall ∝ √weight and √n from the lift equation (PHAK Ch. 5) · true airspeed = KCAS ÷ √σ, σ from the standard atmosphere · gauge error interpolated from the POH rows, held at +2 kt below 69 KCAS · pitch estimate: climb from speed alone = (TAS entry² − TAS slowest²) ÷ 22.6, altitude builds as sin² of the turn so the climb rate peaks at the 45 at climb × π ÷ (2 × time to the 90), climb angle = asin(rate ÷ TAS at the 45), plus a guessed level-flight pitch.
Technique: the 45 check (halfway between entry and the middle of the band) and the next-180 correction. Schematic: the speed and pitch traces through the turn, the chase view. Not SR20 flight-test data.
Derived (labeled): stall ∝ √weight and √n from the lift equation (PHAK Ch. 5) · true airspeed = KCAS ÷ √σ, σ from the standard atmosphere · gauge error interpolated from the POH rows, held at +2 kt below 69 KCAS · pitch estimate: climb from speed alone = (TAS entry² − TAS slowest²) ÷ 22.6, altitude builds as sin² of the turn so the climb rate peaks at the 45 at climb × π ÷ (2 × time to the 90), climb angle = asin(rate ÷ TAS at the 45), plus a guessed level-flight pitch.
Technique: the 45 check (halfway between entry and the middle of the band) and the next-180 correction. Schematic: the speed and pitch traces through the turn, the chase view. Not SR20 flight-test data.
Lazy 8s · v2.0