Does a propeller aircraft that is categorized as CS-25 (EASA Regulation) have the Blue Line (Vyse) mandatory displyed on ASI? I know that would be the case for lighter aircraft (Less than 19000 lbs /8600kg), but my question is related for heavy aircraft (Dash8 example).


1 Answer 1


No, larger aircraft typically don't have such speeds shown on the ASI because they vary significantly with weight. See also Why don't Transport Category aircraft have a listed Vy?.

For the Dash-8 Q400 for example, the $V_{\text{y}_\text{SE}}$ speed is called $V_\text{CLIMB}$:

VCLIMB – Single-engine best rate-of-climb speed.

The following table shows the values for $V_\text{CLIMB}$ as a function of weight:

|  Weight   | VCLIMB |
| 18.000 kg | 130 kt |
| 20.000 kg | 131 kt |
| 22.000 kg | 137 kt |
| 24.000 kg | 143 kt |
| 26.000 kg | 148 kt |
| 28.000 kg | 154 kt |
| 29.000 kg | 158 kt |

As you can see, the values vary too much to show a single blue line on the ASI.

This does not mean that the speed cannot be displayed at all. The Dash-8 Q400 has a Primary Flight Display (PFD) and can show up to 5 speed markers on the speed tape ($V_1$, $V_\text{R}$, $V_2$ and two more called #1 and #2, typically used for $V_\text{FRI}$ and $V_\text{CLIMB}$ respectively during takeoff and initial climb).

Q400 Speed Bugs
(Dash-8 Q400 FCOM - Indicating and Recording Systems)

The resulting markers on the PFD look like this:

Q400 PFD
(Dash-8 Q400 FCOM - Indicating and Recording Systems)

The electronic standby instrument does not show these markers.


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