If you’re familliar with a plane, you should be able to gauge the airspeed sufficiently well to execute a landing just by the way the airflow sounds. Even with ANR headsets you can still hear the airflow – actually, perhaps more so with ANR as it tends to attenuate the lower frequencies the most. It’ll be of course easier with older, draggier types (e.g. a C172, or a PA-28, or the kinds of planes that tend to go to ‘unimproved’ landing areas, your Cubs, Austers, Maules etc). A second indicator is the aircraft’s attitude on approach – look out at the wing tip and see what its angle is relative to the horizon. If you know what it should look like, then if you have an ASI failure then this can help judge whether you’re roughly the right approach speed or not.
Pilot_DAR wrote:
Trim is there to allow you to relieve the flight control load, not to fly the plane because you aren’t
With power, you will need visual references or instruments to fly an airplane, you simply can’t rely on stick position or trim forces to fly it nor the feel
With no power, I am sure you can fly any airplane with just air sound, rudder and trim (and you use these in descending turns as well), the feel of stick is simply function of your speed vs trim position (ref speed)
As far as loss of control in VMC/IMC are concerned both spin and spiral recoveries both involve cutting power, then just question of rudder or aileron?
If unsure, I go for power off and rudder…
Does nobody here fly with a mobile phone or some other kind of GPS gadget? 
If we know our ground speed and can risk a glance out of the window (at trees, water, windmills, smoke…) or if we’ve done a bare minimum of flight preparation, we know our airspeed to the nearest 5-10 knots. That’s near enough for government work – or whenever some clot forgets to remove the pitot’s prophylactic – as long as we have a couple of hundred feet of runway to waste.
Arrive at the airport in the overhead with a minimum of 1000’. Set the engine to about 40-50% (SLPC), 2000 RPM (fixed pitch), 18"/2200RPM (CS prop) or whatever works. But for the aircraft that I fly, these power setting in S&L flight normally lead to a safe flap deployment speed. Deploy flaps all the way to the landing configuration. Slowly pitch up until you are close to the stall (stall warner, buffeting, mushy ailerons), lower the nose just a tad and trim out the remaining control forces. In that configuration you are now about 15 knots above Vs, so you can safely start the approach. Minimise the pitch forces on the control column, fly the approach on power alone.
Ibra wrote:
you simply can’t rely on stick position or trim forces to fly it nor the feel
The trim controls rarely have any forces of consequence, so that is not a factor. Correct, stick position is a poor way to fly a plane. However stick force, and particularly the change in force with change in stick position without retrimming will really tell you a lot about how the plane is flying, and approach to stall. If maintaining the intended flight path were not important, than yes, you should be able to approach stall, and recover to a suitable approach speed by stick feel and the mush feel of the plane alone, eye closed. I know it’s pointless to consider the merits of flying eyes closed, but the point is that change in stick force is telling you a tremendous amount about how the plane is flying – it’s a designed in feature. I have flown two planes with backward stick force gradients near the stall with certain flap settings: the Turbine DC-3, and the Siai Marchetti 1019. Both these airplanes would be very difficult to fly near the stall by feel. The DC-3 seems to have been given a historic certification let on this, and stalling them is discouraged operationally. The Siai Marchetti is not certified in Canada, and I think I understand why!
Yes, your flight path requires either decent visual, or proper use of instruments. However approach to stall can be done by feel alone, flightpath notwithstanding.
A spiral dive recovery with primary use of the rudder will be messy, I’d use the ailerons primarily, coordinating with the rudder as appropriate, and roll out, then recover a straight dive. There won’t be any approach to a 1G stall doing that, the stick force gradient will be telling you something different – don’t over stress it!
Peter wrote:
he Cirrus has envelope protection and will pitch down if airspeed bleeds off too far. Does anyone know what the constraints are on this? One would expect some sort of inhibit e.g. if the engine is developing power, otherwise a pitot heater failure would result in a rapid transition way past Vne, and disintegration.
Newer “digital” autopilots have envelope protection on other airframes, too. The Garmin GFC500/600, the S-Tec 3100, etc. I expect there is no such “IAS indication fault” inhibit, the pilot just has to monitor and disconnect the autopilot in such as situation.
tmo wrote:
A constant speed prop pushed all the way forward is effectively a fixed-pitch prop, right?
Below some power setting, when it will be at its extreme possible pitch :)
Pilot_DAR wrote:
A spiral dive recovery with primary use of the rudder will be messy
I know (I tried) you don’t get much adverse roll from yaw at high speeds but can stop the roll before speed builds up
Pilot_DAR wrote:
The DC-3 seems to have been given a historic certification let on this, and stalling them is discouraged operationally. The Siai Marchetti is not certified in Canada, and I think I understand why!
Back to an earlier point by Airborn_Again, any relationship between certification criteria for GC load envelop and the criteria for yoke force profile?
Or we always look at yoke force on a standard GC/load at stall speeds
Ibra wrote:
any relationship between certification criteria for GC load envelop and the criteria for yoke force profile?
The certification requirement does not allow a deficient stick force gradient for different C of G’s, the stick forces may lighten, but the gradient must always be present as required – specifically to assure correct “feel” for the pilot, and stability.
lionel wrote:
Newer “digital” autopilots have envelope protection on other airframes, too.
Correct – I’m wondering that obviously no pilot of a Cirrus or other plane with this feature does post here. If you fly such a plane, you obviously know by heart what the system does in case of unreliable airspeed. So there must be literally thousands of Cirrus pilots out there who don’t have to think about the answer to this question – but obviously none of them is active here…
I would not necessarily assume these corner cases are well known.
I asked one owner and he said he doesn’t know.
There is stuff online – example – which describes the system. From Garmin, it’s been available for almost 10 years. Here one owner mentions that the underspeed protection uses the stall warner and is thus immune from a pitot failure, but I can’t find anything online on ovespeed and pitot failure other than a lot of stuff applicable to large aircraft.
Note also the obvious: a failed ASI is not the same as a blocked pitot. Either stops the pilot seeing the airspeed, but only the latter will affect overspeed protection because airspeed will be sensed with a separate differential pressure sensor connected to the pitot+static. AFAIK there is no such thing as an “encoding ASI”.
