Q400 minimum clean speed
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Q400 minimum clean speed
Could some q400 drivers enlighten us as to what minimum clean speed they use on the q400?
There seems to be some variation between operators, with flybe using a set speed of 170(190 icing) and others such as Colgan using vfto (Vfto +25 icing).
It would be interesting to know what operators such as horizon, air Canada express or any others use. Bombardier seems rather vague on the matter.
There seems to be some variation between operators, with flybe using a set speed of 170(190 icing) and others such as Colgan using vfto (Vfto +25 icing).
It would be interesting to know what operators such as horizon, air Canada express or any others use. Bombardier seems rather vague on the matter.
Here, it depends on whether icing conditions are present or not (those take a speed increment of about 20kIAS depending on situation).
180kIAS is a good figure for most conditions and ATC is usually happy with this. Lower is possible in non-icing conditions; turbulence and icing together on the other hand might cause a crew to prefer 190-200kIAS for more speed margin (min speed is typically around 170kIAS in icing).
180kIAS is a good figure for most conditions and ATC is usually happy with this. Lower is possible in non-icing conditions; turbulence and icing together on the other hand might cause a crew to prefer 190-200kIAS for more speed margin (min speed is typically around 170kIAS in icing).
At the other end of the flight regime, 130 kts is the minimum flap retraction speed.
But that is with full takeoff thrust blowing over the wings - and is the minimum limit, not a goal. And likely requires a similar increment for icing conditions.
But that is with full takeoff thrust blowing over the wings - and is the minimum limit, not a goal. And likely requires a similar increment for icing conditions.
PatternIsFull, is that irrespective of weight and icing conditions in Your company?
For a heavy aircraft, this seems rather on the slow side, seeing that V2 without ice increment at flaps 5 and MTOW is already nearly 140kIAS (with ice, above 1000ft, it even shows 158kIAS).
Here, we have a speed called Vfri (Flap Retraction Initiation), which is at V2+10 and therefore takes weight, icing conditions and a possibly deiced wing (as well increasing the V speeds in my company) into account. It must obviously be achieved before starting to raise the flaps. As a nice little side effect, Va is nearly equal to V2+10 for a given flap setting (+/-2kIAS), so in a go around, raising the flaps at just a bit above Va with NTOP set is appropriate as well - no need to tamper with those speed bugs in an already high workload situation.
For a heavy aircraft, this seems rather on the slow side, seeing that V2 without ice increment at flaps 5 and MTOW is already nearly 140kIAS (with ice, above 1000ft, it even shows 158kIAS).
Here, we have a speed called Vfri (Flap Retraction Initiation), which is at V2+10 and therefore takes weight, icing conditions and a possibly deiced wing (as well increasing the V speeds in my company) into account. It must obviously be achieved before starting to raise the flaps. As a nice little side effect, Va is nearly equal to V2+10 for a given flap setting (+/-2kIAS), so in a go around, raising the flaps at just a bit above Va with NTOP set is appropriate as well - no need to tamper with those speed bugs in an already high workload situation.
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Thanks for the inputs, gents. really appreciate it.
Obviously there is a difference between climb speeds (v2, Vfri and Vfto) and approach speeds due to thrust, but the question really is what is the slowest airspeed you can fly on descend/approach/hold without getting a "check speed" call or FDM event? Both Boeing and Airbus are pretty clear on minimum clean speeds: Bombardier not so much.
Bombardier does publish max endurance speeds for the hold which are a knot or two above Vfto, and thereby much lower than the 160/170/180 knots mentioned here. (let's leave icing out of it for the moment while agreeing that it adds a good 20-25kts to any speed except v2 up to 1000'agl.)
For a given weight, say 27 tonns (54k lbs) Vfto is 152 and published clean holding speed is 154. A company that has a minimum clean speed 15-20 knots higher would need to correct their fuel burn in the hold accordingly.
Or, to put it another way, is there a good argument for allowing the hold (with it's level flight and varying bank abgles) to be flown at Vfto but placing a higher restriction on the final approach which by it's very nature (unless finishing with a circling maneuver) is very limited in bank?
Appreciate any further input.
Obviously there is a difference between climb speeds (v2, Vfri and Vfto) and approach speeds due to thrust, but the question really is what is the slowest airspeed you can fly on descend/approach/hold without getting a "check speed" call or FDM event? Both Boeing and Airbus are pretty clear on minimum clean speeds: Bombardier not so much.
Bombardier does publish max endurance speeds for the hold which are a knot or two above Vfto, and thereby much lower than the 160/170/180 knots mentioned here. (let's leave icing out of it for the moment while agreeing that it adds a good 20-25kts to any speed except v2 up to 1000'agl.)
For a given weight, say 27 tonns (54k lbs) Vfto is 152 and published clean holding speed is 154. A company that has a minimum clean speed 15-20 knots higher would need to correct their fuel burn in the hold accordingly.
Or, to put it another way, is there a good argument for allowing the hold (with it's level flight and varying bank abgles) to be flown at Vfto but placing a higher restriction on the final approach which by it's very nature (unless finishing with a circling maneuver) is very limited in bank?
Appreciate any further input.
Of course, if one wants to maximize endurance while in a hold, flying at Vfto is strongly advisable. But this comes at a price: flying straight and level at Vfto will see pitch above +5°, which we are encouraged to avoid due to passenger comfort (our company considers the Dash a somewhat uncomfortable aircraft for passengers and therefore has provided whole libraries on how to somewhat mitigate the noise and vibration lebels). So while it would be possible to reduce below 180kIAS in a holding when weight and icing conditions permit, this is not normally done.
I would also assume that this is for standardisation reasons: when ATC calls several DH8 to fly Minimum Clean, this could result in speeds between 135 and 190kIAS depending on weight and icing conditions applicable for the individual aircraft. Also, when entering or leaving icing conditions, this minimum clean speed will change by the mentioned 20kIAS. All this has the potential to surprise the ATCO and mess with his sequencing. So Min Clean is 180kIAS here, as this is good for every weight and icing conditions as long as no turbulence is involved; if another, lower speed is required, it takes just a word from ATC.
I would also assume that this is for standardisation reasons: when ATC calls several DH8 to fly Minimum Clean, this could result in speeds between 135 and 190kIAS depending on weight and icing conditions applicable for the individual aircraft. Also, when entering or leaving icing conditions, this minimum clean speed will change by the mentioned 20kIAS. All this has the potential to surprise the ATCO and mess with his sequencing. So Min Clean is 180kIAS here, as this is good for every weight and icing conditions as long as no turbulence is involved; if another, lower speed is required, it takes just a word from ATC.
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Thanks Tu.114
While I can understand your comments about pitch and how they relate to company policy, aircraft pitch in itself does not offer much of an argument in terms of aerodynamics, performance or safety. Right now those are my concerns more than to what extent passengers prefer a clean 8 degree ANU on a Boeing or a clean 5 degree ANU on a Bombardier.
As for ATC, those are certainly valid points for everyday operation into larger airports but again seems to distract from the core of the issue.
There are obviously regulations which limit the absolute minimum speed to Vref, but I'm sure most will agree that flying Flap 0 Vref from 15 miles (for whatever reason) does not sound like a good idea.
So the question remains at what speed, on approach and with flaps at 0, will a line-check result in a non-satisfactory remark about the speed being flown?
I understand the issues of icing, INCR REF SPEEDs, aircraft attitude and ATC restrictions, but if we can ignore those for the moment, where do we end up with the various operators?
While I can understand your comments about pitch and how they relate to company policy, aircraft pitch in itself does not offer much of an argument in terms of aerodynamics, performance or safety. Right now those are my concerns more than to what extent passengers prefer a clean 8 degree ANU on a Boeing or a clean 5 degree ANU on a Bombardier.
As for ATC, those are certainly valid points for everyday operation into larger airports but again seems to distract from the core of the issue.
There are obviously regulations which limit the absolute minimum speed to Vref, but I'm sure most will agree that flying Flap 0 Vref from 15 miles (for whatever reason) does not sound like a good idea.
So the question remains at what speed, on approach and with flaps at 0, will a line-check result in a non-satisfactory remark about the speed being flown?
I understand the issues of icing, INCR REF SPEEDs, aircraft attitude and ATC restrictions, but if we can ignore those for the moment, where do we end up with the various operators?
Originally Posted by Cloud Surfer
At what speed, on approach and with flaps at 0, will a line-check result in a non-satisfactory remark about the speed being flown?
Of course, this situation is rather theoretical. Flying that slow without any drag out is not really easy when on a glide path; I do doubt that unless one has established that speed in level flight before intercepting the glide, it is even possible to slow down that much without dropping gear and flaps or increasing prop RPM. Also, why would one want to do this unless the flaps are stuck at 0 and one is commited to a flapless landing?
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Tu.114
You're absolutely right.
Vapp is the minimum speed on approach, plus icing increment if required.
Above and beyond Vapp, company policy decides and my impression is that q400 operators tend to fall into one of two categories:
a) those that set Va (1.23vsr) as minimum clean approach speed,
b) those that set a hard speed (ex. 180/190) to cater for whatever mix of scenarios they meet in their daily operations.
Thanks for taking the time.
You're absolutely right.
Vapp is the minimum speed on approach, plus icing increment if required.
Above and beyond Vapp, company policy decides and my impression is that q400 operators tend to fall into one of two categories:
a) those that set Va (1.23vsr) as minimum clean approach speed,
b) those that set a hard speed (ex. 180/190) to cater for whatever mix of scenarios they meet in their daily operations.
Thanks for taking the time.
