Two questions: Terrain Warning and Severe Icing

[ukmatt]

Hi,

I flew into United into Las Vegas this morning and was sitting towards the front (row two) and I have a couple of questions.

For the majority of the flight I was listening to Channel 9 so I could hear the ATC communications from the flight deck. At one point another aircraft requested clarification on where severe icing had been reported and based on the response (which I think was an altitude range where it has been observed) ultimately the crew told the controller they were "not certified" to fly in severe icing. Is that an aircraft limitation or a crew limitation?

Second question - at one point I was not listening to channel 9 as we were well into the approach. This was a fairly normal route where we fly over Lake Mead and then take a big left turn to head West into LAS. As we made the turn, we could clearly hear a horn and a terrain warning (something like "Terrain, Pull Up"). Is this a common thing? Seems odd that a standard approach would involve a terrain warning.

Thanks!

[wheelie my boeing]

No aircraft should be flown in severe icing. They are not designed for it and prolonged exposure could and probably would have fatal consequences. Hence the pilots wanted to avoid it if at all possible... Best thing to do would be either don't go through it, or if you have no choice then get through it as quickly as possible so find out (again, if possible) where it starts and where it finishes in relation to altitude.
Not sure about your second question. There are many different bells and whistles in the cockpit and depending on aircraft type it could have been anything. Glideslope warning, autopilot disconnection, multiple warning/horns at the same time (like loss of airspeed due wind fluctuation resulting in "speed speed speed" at the same time as autopilot disconnection etc). Whilst it may have felt like a standard approach it's difficult to decipher you're altitude from the cabin, they may have been lower than they should have been but could visually see the terrain so ignored the warning. Many possibilities.

[ukmatt]

No aircraft should be flown in severe icing. They are not designed for it and prolonged exposure could and probably would have fatal consequences. Hence the pilots wanted to avoid it if at all possible... Best thing to do would be either don't go through it, or if you have no choice then get through it as quickly as possible so find out (again, if possible) where it starts and where it finishes in relation to altitude.


Thanks - the complete exchange between the pilot and ATC suggested they were not actually allowed to go through an area of severe icing (they specifically said "not certified for severe icing") after ATC confirmed an altitude range and confirmed they'd be directed to descend quickly through that area.

It surprised me that a commercial aircraft and crew could fly without being certified for an atmospheric condition that could occur...

Not sure about your second question. There are many different bells and whistles in the cockpit and depending on aircraft type it could have been anything. ... Whilst it may have felt like a standard approach it's difficult to decipher you're altitude from the cabin, they may have been lower than they should have been but could visually see the terrain so ignored the warning. Many possibilities.

It was definitely a terrain pull up type warning as it was clearly audible... the conditions were good at the time in terms of visibility so I have no doubt they could visually see the terrain but again, it surprised me they'd get close enough to get a warning to pull up!

Thanks for your response.

[PEI_3721]

Terrain incident number 8 (http://www.icao.int/fsix/_Library%5CTAWS%20Saves%20plus%20add.pdf) was at Las Vegas ! Operator unknown.

[de facto]

Terrain warning may happen at some non standard ICAO airports where maneuvring requires close positionning to terra firma.
Such maneuvre is to be accomplished with a minimum visibility provided by the airport/local CAA.

No aircraft is certified to fly into severe icing,but it does not mean it can not for a certain time deal with icing accretion.
The term of sever icing is quite 'subjective' when given by pilots just as the description of moderate turbulence.
Icing can affect a small type of aircraft with inexperienced crew with more icing that they ever seen before and will pirep it as severe icing.
Others may call for moderate turbulence when what they have is light and want to have ATC favor to climb to a higher level earlier.
Speed loss/increase may be a better info to be relayed between pilots to judge the 'severity' of such turbulence.

If icing is reported as severe in an area known for such icing then your pilots were planning ahead and tried to avoid picking up ice before starting a possible maneuvring problematic approach.(not familiar with Vegas though).