as many of you know, my app In-Flight Assistant lets you set V1, V2, and VR speeds so your “co-pilot” calls them out during takeoff. I’ve had quite a few requests to provide a calculator in the app to let you know what those speeds need to be, but the problem is that the formulas for calculating them are quite complex and often are an airline’s secret business knowledge.
So, I had the idea - what if we slowly but surely “crowdsourced” the values for all the airplanes in IF by experimenting ourselves (or consulting actual manuals if we have them 😃), and thus at least find “close enough” speeds? I’d then make the table publicly visible, and add it to the app as a calculator at no additional cost, and we’d all benefit from it!
To make sure we’re all on the same page here, here are what the speeds mean:
V1: the “point of no return” speed - once you reach this speed, you can no longer abort take off but must take off, even if there’s an emergency.
V2: the speed at which you will be able to safely gain altitude even if you lose 1 engine - a typical climbing speed is V2+15.
VR: the speed at which you should gently but firmly pull back on the yoke to lift off the runway.
I’ve made a Google Spreadsheet for this purpose that anyone with access can edit. Here it is.
Here’s a proposal for finding the speeds by experiment - but this may be completely off, so if some of you real pilots have a better idea how to find the correct speeds, I’m all ears.
- Let’s all do our experiments on a “normal” 8500 ft. runway: KMIA 08L with no wind.
- Set up your weight based on the table cell whose value you want to determine.
- Set flaps to 5° (or equivalent - in an Airbus, set it to 1)
- Assume a temperature of 15° (normally temperature would influence the V-speeds as well, thanks @CJ12 for this point.
V1 - Start on one end of the runway, accelerate with 95% N1 (this is not 95% throttle), and then figure out the speed at which you no longer can stop before the end of the runway with brakes only.
V2 - Find your stalling speed while climbing at 95% N1 and add 10 knots
VR - Find the speed at which you can pull back on the yoke and gently take off at 95% N1 - you shouldn’t be shooting up like a rocket, nor should it take you forever to get your nose off the ground.
If you would like to take part in this experiment, shoot me a quick PM with your Google account email for edit access to the spreadsheet!
Hope I’m not forgetting something incredibly obvious and important here. 🤣 Let me know if you have any questions!