tcasdescend

After watching air crash investigation:

Why does the stall and stick shaker warning sound even though pitot tubes are blocked?

Why does the too low terrain warning sound even though the altimeter may be faulty?

If a plane falls down from the sky with the nose pointed up, what will the airspeed indicator indicate?

sevenstrokeroll

the stick shaker etc is not part of the pitot system...usually it requires an angle of attack sensor/vane to work

the terrain warning has nothing to do with the barometric altimeter...the earliest forms had a special radar set to measure the angle of the approaching terrain

the airspeed indicator would indicate very low or no airspeed if the plane was falling with the nose up

ZFT

GPWS used the radio altimeter for height with no 'look ahead'. It just calculated terrain height closure rate.

IGh

Questions posed, regarding post-mishap simulation:
Re' the TV's mishap _simulations_, this points to the investigative-errs after several famous accidents, with the manufacturer attempting steer the investigation: using a simplified "model" to guess about the nature of INITIAL upset, interval of uncontrolled dive, and the final recovery/breakup/impact.

There has been an ongoing problem, over decades, with the Boeing post-accident simulation trials, usually done using the M-Cab there in Renton. The disputed _sim_ conclusions, sometimes in open contradiction to the mishap pilots' description, have swayed the investigators toward an erroneous conclusion. [This issue of post-accident misleading "simulation" deserves more study by the NTSB: from AA Flt One/ 1Mar62, to TWA841/4Apr79, to Palm 90/ 13Jan82, to SilkAir Mi-185/ 19Dec97.]

The mishap-FDR might record IAS (sometimes not, sometimes FDR captured only filtered-averaged airspeed-data), but that won't show you EXACTLY what the mishap-pilot saw on his Airspeed Indicator. For an answer to that specific NOSE-UP descent question, some test pilots can perhaps describe their experience. My first inclination, for review, would be the case Bac 1-11 nose-up test data: Checking data from two test mishaps [BAC 1-11 G-ASGH /22Oct63 (fatal) , & G-ASJD /20Aug64] there are pilot comments about suspected erroneous AOA- "Incidence" indication, but no comments about erroneous IAS.

Other example-mishaps, with an interval of slow-speed nose-up uncontrolled descent:

-- Aeromexico /11Nov79, DC10 NTSB/AAR-80-10

-- ABX / 22Dec96, DC8-63, NTSB/AAR-97-05 or DC-8 Mishap on 12 Dec 1996 N827AX -Stall Recovery in Mountainous Terrain | APS Emergency Maneuver Training

-- Spirit 970 / 4Jun2002 MD8 CRZ, ntsb's description Untitled Page, ntsb's conclusion about Autothrottles with erroneous-EPR displayed at Limit while actual-N1 rolled-back toward Idle CHI02IA151

B717 / 12May05 and various other similar pitch-upsets
Pitch UPSET +/-20deg, opposing ColumnForce=100Lbs

-- West Caribbean /16Aug2005 MD82 night CRZ; Report: West Caribbean MD82 at Machiquez on Aug 16th 2005, did not recover from high altitude stall; AAR is mostly Spanish language Rapport Crash West Caribbean (espagnol) but Anexo 5 is BEA’s FDR readout, Anexo 6 (pdf-pgs 187-246) is an ASRS database of 22 events with pilots’ description (and misperceptions) of MD-80 high altitude stalls; Anexo 7 (pdf-pgs 247-271) Boeing slides (24) on various factors in High Altitude Stalls (ice crystals, higher AoA induced compressor stalls that were NOT audible to human pilots)

Re' the 16Aug05 slow-spd DAC-pitch upset, there is an _ACI_Mayday_ video about that nose-up descent (this drama-simulation failed to explain reasons for the human's misperception of duel-engine flame-outs):