What do you do if you lose speed indication?

[swood721 28]

Loss of airspeed is a memory item at my airline. Depending on flap configuration the procedure is to turn all automation off (autopilot, auto throttles and flight directors) then set 4 degrees pitch and 75% N1 for flaps up or 10 degrees pitch and 80% N1 for flaps extended. From there, run the QRH. This is for the 757/767 only.

[Himbi 1]

The best thing you can do is that you just to nothing. Maintain altitude, thrust setting and pitch.

[berts 97]

22 hours ago, Bluestar said:

I realize my military training was different than civilian training, and this is not a criticism of civilian instruction.  One of the maneuvers that I was required to perform on partial panel was to do a spin and roll out on a designated heading.  It has been my experience that even the best attitude indicators will tumble on occasion.   

 

You are right about old-fashioned attitude indicators tumbling, but in my experience the main difference between civilian and military training is commercial pilots don't drop bombs; only the odd bombshell when they get it wrong! 

Seriously though, I would be very surprised to learn that any partial panel or recovery from unusual attitudes training that is undertaken in a jetliner/simulator involves a spin and roll out onto a designated heading.  The priority is to recognise and confirm the situation, such as a stall or jet upset, and then recover from it safely by disconnecting the automatics and flying the aircraft manually -  without hitting the ground or overstressing the airframe (either one of which is bound to upset the passengers!).

[BlueStar 323]

3 hours ago, berts said:

The priority is to recognise and confirm the situation, such as a stall or jet upset, and then recover from it safely by disconnecting the automatics and flying the aircraft manually -  without hitting the ground or overstressing the airframe

Bert,

My military training was all about dealing with spatial disorientation in a confusing and stressful environment which is exactly what you have described above.  This training has served me well in my career as a commercial pilot. 🙂

Grace and Peace, 

[Paul_Smith 92]

On 11/4/2018 at 10:17 PM, paulyg123 said:

Downscc.  Are you saying on a recent Boeing plane the pilot and copilots speeds are determined by separate systems?  If that is the case I need not worry about losing my speed readings,  I’d just check with my co pilot.   Let me know if  this is the case

Yes and no. They can and indeed should be on separate sources but that doesn't mean they have to be. The real problem comes when your instrument and your co-pilots are showing different readings; Which one do you trust? A number of accidents have been attributed to the senior pilot trusting their own instrument instead of being suspicious of both. Some people associate this behavior with one of the known issues with IFR training in that it is usually obvious which instrument can no longer be used. This leads people to think that if there is no fault flag (or post-it covering the display), then it is still safe to use.  

The basic cockpit instruments mean that any and every change should show up on at least two instruments. It also means that the total failure of any instrument is no more then inconvenient since the information lost can be deduced from the remaining instruments. 

Partial failure (ie a device giving reasonable but wrong readings) should be detectable by verifying every change against other instruments. Say you notice your airspeed starting to drop, you know that airspeed is pitch plus power so one of them must also be changing. Which one and why? If your pitch is changing then that would show up on attitude, altimeter and variometer, if your power is changing (and you don't have engine instruments that show this) then you would still see attitude changes and feel trim changes and hear engine sound changes.

 

[berts 97]

On 11/6/2018 at 2:30 PM, Paul_Smith said:

The real problem comes when your instrument and your co-pilots are showing different readings; Which one do you trust? A number of accidents have been attributed to the senior pilot trusting their own instrument instead of being suspicious of both.

This is precisely what happened in the Mumbai accident I mentioned earlier.  One ADI apparently failed due to a faulty transistor with no failure flag and as the instrument slowly toppled the handling pilot relied on it instead of cross-checking with the other pilot's ADI and the Standby instrument and as a result the aircraft was eventually lost with all souls. As Wilhelm said, this accident was caused by a simple instrument failure which probably resulted in spatial disorientation of both pilots in a confusing and stressful environment.

[captainsazzman 83]

On 11/5/2018 at 1:30 AM, Chock said:

This is pretty much the case for every airliner...

 

 

 

All those checks are nice and cute, but why not also ask ATC what speed they seeing?

[Budbud 227]

Hello,

ATC would give an ground speed, not an aispeed. Depending on the wind the different may get you out of the flight envelope.

[Paul_Smith 92]

1 hour ago, captainsazzman said:

 

 

All those checks are nice and cute, but why not also ask ATC what speed they seeing?

As a pilot you care only about how fast the air is moving over your wings and the ATC doesn't know that. They only know what your transponder tells them and if they you on actual radar, maybe they can work out (roughly!) what your ground speed is, but as a pilot, you don't care about your ground speed except when you want to calculate an ETA.

As for cute? Cute is pretty puppys playing or kittens cavorting. Knowing what you need to do to stay alive is not cute, its Darwin.

 

 

[MarkW 1,491]

Blackbox711 has a great video on using pitch and power when losing speed information.  This is for the FSL airbus, however, the lesson transfers to any aircraft.

 

 

[BlueStar 323]

3 hours ago, captainsazzman said:

All those checks are nice and cute, but why not also ask ATC what speed they seeing

ATC radar speed is an estimate based on time and distance across the ground updated with every sweep of the radar.  The aircraft can be climbing straight up indicating 300 knots and the radar will show zero ground speed.  The farther away the radar target is from the radar the less accurate the radar is.  Radar speed of the aircraft is only useful to the controller for separating aircraft.

"cute" 🤣

Grace and Peace,

[Budbud 227]

11 minutes ago, Bluestar said:

Radar speed of the aircraft is only useful to the controller for separating aircraft.

Even for separation they may rely on the aircraft air speed and the pilots, instructing them to maintain an IAS.

Edited November 8, 2018 by Budbud

[Ephedrin 418]

On 11/6/2018 at 5:30 AM, Bluestar said:

This training has served me well in my career as a commercial pilot. 🙂

Because you found yourself that often spinning your 707? XD I knew there was this guy barrel rolling it 😄 but....

😜

[BlueStar 323]

2 hours ago, Ephedrin said:

Because you found yourself that often spinning your 707?

No, but I have had to deal with spatial disorientation from time to time through the years.  I participated in an FAA/Military study on spatial disorientation back when every one was wearing "brown shoes" and it screwed me up for a month. 🤣

Grace and Peace, 

[PopsBellNC 21]

Being a continuous, life-long, student (i.e., you never graduate) of the "What If? School of Flight", a 10 year-old Garmin eTrex handheld tossed in your bag can provide a surprising amount of useful information in this situation. These are the types of things that paranoid pilots play with (recall: "Paranoia is Perfect Awareness!" ) while 6 hours out over the Pacific. 😉