View Full Version : E170/175 Vref Ice speeds
Dockjock
6th Jun 2007, 03:23
When ice is detected on the E170/175 for more than 10 seconds (approx.) the anti ice systems are switched on and amongst other annunciations, an EICAS message "STALL PROT ICE SPEEDS" in cyan is displayed. This requires the crew to use increased Vref speeds regardless as to the landing weather ie. may encounter ice on departure, fly for 3 hrs and land in +30C temps, and still are required to use ice speeds.
Are there similar requirements on other modern jet types?
The E170 was the first aircraft where I encountered this requirement.
Mutt
Clandestino
7th Jun 2007, 18:09
Sounds interesting. On ATR, every time flight controls anti-icing is turned on, stickshaker activation AoA goes down (if I recall correctly, it's from 12.5 to 7.5° AoA) and higher approach speeds have to be used. However, if conditions during approach are not conductive to icing and aircraft is visually confirmed to be free of ice accretion, icing AoA could be reset and normal approach speeds used.
Are you sure that system on E-jets can't be reset inflight?
FE Hoppy
7th Jun 2007, 18:41
Embrear 145 has the same.
This is under review and may change with future epic updates.
chasing767
7th Jun 2007, 20:45
Clandestino,
I happened to fly ATRs for some time and have transitioned to E175 as well.
You can not cancel this High Speed Imposition in any way.U just got some ice in Helsinki and continue down to Athens with such a thing. Not only speeds are higher but N1 idle is set at higher level too - this doesn't make things easier when you wanna slow down.
it may only be so due to software as someone suggested but I have another idea.check this out:
I know of crew who flew an ATR with this green AOA caption illuminated as they were in Icing conditon. once cleared of the ice they switched all systems off( 3 and 2 ) but didn't cancel the green caption. approaching the airport during sunny summer day they didn't realize they had this light still illuminated ( old or burnt bulb might have also been the factor here...) and set normal i.e. regular , non icing speeds. the plane was heavy as heavy ATR could be :-) and during the flare they got shaker warning. believe it or not.
no surprise if EMB designer chose to make it safer this way although it's kind of annoying to fly at 150 kts in beautiful wx with no apparent reason.
what do you think?
best rgrds
Embraer have strange methods of dealing with a number of things, this is one of them, they are protecting the aircraft for ice build up on unheated surfaces.
Mutt
737 (NG) has Vref-ice also, as the stall logic is reset to a raised datum by use of anti-ice measures.
I`m not on the 145 anymore, but used to be. Isn`t it mainly because the stickshaker and pusher operate at a slightly higher speed after the aircraft has encountered icing conditions?
Clandestino
9th Jun 2007, 06:24
Hi Chasing767
I don't have a problem with believing your story because I've been there, done that, scared myself ****less. Lucky me, the cricket and the shaker went off when we were about 2-3 inches above concrete so I had no time to botch up the landing. We have also set speed bugs according to normal speeed schedule, picked up some light ice during the descent and when we turned anti- and de-icing off, decided to wait with icing AoA reset till the ice melts - you already know that we forgot to do that.
I don't know how approach speeds are set on E170 but I'll assume they're set automatically by FMS. If I guessed it correctly, it would be easy to install system similar to ATR's (ice evidence probe and manual confirmation that airplane is clear of ice), connected to FMS so as long as icing AoA is on, FMS sets higher speeds and as soon as it's reset, bugs go down.
It's all very well to have some extra knots when you have ice on the plane but those extra knots over threshold turn into extra runway used for stopping. No big deal if you land on 2500m+ of tarmac, but if your destination is not blessed with long runway, these extra knots might adversely affect your payload.
Cheers, C.
chasing767
14th Jun 2007, 08:37
Clandestino,
the approach speeds are entered via the keypad directly by the pilot. so the pilot is ultimately responsible for enetring the proper icing data - not only checking it.ch767
Avi8tor
14th Jun 2007, 14:22
J41 has the same system. Just better than the EMB that it can be cancelled in-flight. EMB is a pain when u climb out of Cape Town and then have to land in Windhoek and +30 with ice speeds.