Flying Without Airspeed

[willedoo]

Link to an article about flying without airspeed indication. Discusses ice issues & the loss of Air France 447 among other things.

 

http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=bca&id=news/bca/2012/03/01/BC_03_01_2012_p34-422240.xml&headline=Flying%20Without%20Airspeed

 

Cheers, Willie.

 

 

[metalman]

My first flight in an RAA aircraft I noticed some white plugs on the inside of the canopy, I had a GFPT but bugger all hours, we did one circuit in the golf and on the second one the FI says "are you flying the attitude", and promptly sticks a white plug over the ASI. After a couple of laps I had the airspeed nailed on 60 knots every time , apart from the confidence boost I've never had a problem with "eyes outside" , although I've found it hard to find a reference point in pusher aircraft like the Seeker or drifters I reckon with enough hours in them you get the feel for them

 

Cheers mat

 

 

[cficare]

good words Mat

 

many students do many hours and dollars because they are not aware that (for whatever power setting)...attitude determines airspeed.

 

 

[Coop]

It may never happen to you, but in 40 years of flying for fun I've had two occasions where I've had to fly without an ASI. The first was in a glider where the plastic tube connecting the pitot to the ASI came adrift (got hard in the sun and then someone reached in to adjust something else and partially dislodged it without realising it). At normal cruise (45-55 knots) it was reading 25-30knots. Didn't notice it until I came off tow- your eyes are glued to the tug when on tow and he sets the speed anyway. There was no major drama flying without it- just opened the clear vision port during final and made sure we had plenty of wind noise on the approach which was deliberately a little on the fast side.

 

The second was in the Auster- we had one of those little flaps that are supposed to seal the pitot and lift up when the airflow increases on takeoff. Somehow a bloody wasp got around this and built its nest at the bottom of the pitot tube where it joins the rubber pipe. Noticed zero airspeed on take-off but wasn't sure if we had enough room to stop (the Auster's brakes are known as "influencers") so we kept going. As soon as we came off the ground the ASI began pretending it was an altimeter (which, I guess, it was, with a blocked pitot) so I ignored it. At circuit height we leveled and set cruise power and on approach just set the power to where it normally sits and we landed without flaps as the Auster has a fairly low flap extension speed. Again, it wasn't difficult to do. After landing we removed the pitot tube and disconnected the rubber tube and there was the mud plug containing a caterpillar doing an "Alien" impersonation. We now use a proper pitot cover with "REMOVE BEFORE FRIGHT" embroidered on it. ;-)

 

I suspect it gets more difficult the heavier and slicker the machine. But then, as the chap in the article cited above says, those machines often have multiple sources of speed/attitude information, most of which are a sufficiently accurate approximation to airspeed to ensure safe flying.

 

Coop

 

 

[sixtiesrelic]

Flying the DC-9 and 737 was just the same... power and attitude you got the required speed. We learned them off by heart.

 

 

[metalman]

something else I was thinking about regarding "flying with out airspeed", I had read somewhere about flying below the posted stall airspeed ,so I went up in a tecnam to try it out , ended up with a balancing act between the throttle and the stick position and managed to get it holding height and indicating around 20kias, I know the pitot wouldn't have been getting the right airflow but it was a good exercise in controlling the stall with power and the stall stick position ,went up in a savvanah recently and had a play around ,ended up with the ASI reading nothing, which of course doesn't mean we had none (airspeed) but we were really going slow, all good fun and I think you can learn a lot more about your aircraft at the slow draggy end of the envelope!

 

Mat

 

and something I noticed in the Savvanah is it dropped the left wing in a S and L stall everytime, is that standard for them?

 

 

[dazza 38]

Pilots alway try and flnd out how fast there ride goes.I think it is best to find out how slow there ride goes.:D

 

 

[Wayne T Mathews]

Pilots alway try and flnd out how fast there ride goes.I think it is best to find out how slow there ride goes.:D

Finding out how fast your aircraft goes isn't all that hard to do. Just push the throttle forward on a calm day and hope the controls don't flutter. Finding out how slow your aircraft goes is a tad more complicated. But then I'm prejudiced. The first aircraft I ever poled was a high performance aircraft at the bottom end of the speed spectrum.

 

 

[metalman]

The first aircraft I ever poled was a high performance aircraft at the bottom end of the speed spectrum.

kinda cryptic, do tell ,what what it?

 

 

[Wayne T Mathews]

Back in '72, I was a new (read, inexperienced) flight fitter on Iroquois. We were on an exercise supporting the SAS in Western Australia and an Army Captain let me go up with him and pole his Pilatus Porter. Sort of like a TIF, only different... I've never been the same since...

 

 

[metalman]

I haven't had a "I never be the same again " flight yet, but I'm hoping for it,

 

actually every new aircraft is life changing,,,

 

 

[Coop]

Mat, if you are having fun messing about at the slow end of the spectrum, then you have probably discovered "lateral damping" (or the lack of it). At normal speeds when a wing is deflected down it experiences a temporary increase in AoA and increased lift while the other wing experiences a temporary decrease in AoA and decreased lift. This asymmetric lift resists the movement of the wing, and "damps" the rolling (it's a component of the "lateral stability"). But as you approach the stall, a deflection can take the downgoing wing temporarily beyond the stall angle, and you get a loss of lift, not an increase. So the aircraft begins to feel like it is balanced on a knife edge, with any wing drop tending to result in that wing going down more unless an opposite rudder input pushes the wing forward and momentarily reduces the angle to just below the stall angle, restoring lift. Of course, this also retards the other wing and may take it beyond its stall angle, and so it tries to go down.... and so it goes on with you pedalling the rudders to prevent either wing from dropping until you either reduce the angle overall, or you momentarily increase the overall AoA and the wing stalls completely.

 

Cheers,

 

Coop

 

 

[metalman]

Mat, if you are having fun messing about at the slow end of the spectrum, then you have probably discovered "lateral damping" (or the lack of it). At normal speeds when a wing is deflected down it experiences a temporary increase in AoA and increased lift while the other wing experiences a temporary decrease in AoA and decreased lift. This asymmetric lift resists the movement of the wing, and "damps" the rolling (it's a component of the "lateral stability"). But as you approach the stall, a deflection can take the downgoing wing temporarily beyond the stall angle, and you get a loss of lift, not an increase. So the aircraft begins to feel like it is balanced on a knife edge, with any wing drop tending to result in that wing going down more unless an opposite rudder input pushes the wing forward and momentarily reduces the angle to just below the stall angle, restoring lift. Of course, this also retards the other wing and may take it beyond its stall angle, and so it tries to go down.... and so it goes on with you pedalling the rudders to prevent either wing from dropping until you either reduce the angle overall, or you momentarily increase the overall AoA and the wing stalls Coop

That explains the feeling very well, short sharp jabs on the rudder to keep it S&L, with a bit of height it is a great to go where a lot of pilots fear to tread. It's a great lesson on stall stick position , it can be the difference of a few millimetres between stalled and unstalled, all good stuff and should be taught.

Mat