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PHD. MBA. MHS. Type rated on A350, A330, B777, B747-400, B747-200, B757, B767, B737, B727. International Airline Pilot / Author / Speaker. Dedicated to giving the gift of wings to anyone following their dreams. Supporting Aviation Safety through training, writing, and inspiration. Fighting for Aviation Safety and Airline Employee Advocacy. Safety Culture and SMS change agent.

Tuesday, June 21, 2011

A330 Glide Ratio

An interesting discussion has been floating about concerning the glide ratio of the A330.

Airbus recommends that with an all-engine flameout to fly a speed of 300/.82M -- the optimum relight speed. This speed will produce a glide of approximately 100NM from FL400 which equates to a 15:1 glide ratio.

Then someone asked, "What is the glide ratio for green dot?"

Have you ever been asked a question that there is no answer? 
This is one of those times. 

After talking with my friend at Airbus he reminded me that "green dot" is the speed that provides the best lift-to-drag ratio when the airplane is in a clean (gear and flaps up) configuration. And green dot is a function of weight and altitude. Therefore, there isn't one answer... but many.
For non-airbus pilots: Why do they call a speed green dot? 

Because, there is literally a green dot on the speed tape for quick reference. As indicated below... around 249 knots.

For those inquiring Airbus minds... just thought you'd want to know.

News Flash: This update is three days after the post. Interesting data has been coming in. A330 Pilots are and coming up with more green dot data and sending it my way.

250KIAS (307 TAS)  & 1100 ft/min:  28:1 glide ratio
307KTAS = 31109 ft/min    /   1100  =  28.28

FL220 394,000 pounds:
300kias/430TAS & 1900'/min   23:1
430kts=43573 ft/min  / 1900=  22.9  

Enjoy the journey!



  1. Hope you never need that particular piece of information!

  2. So interesting. Does this sort of thing exist in small plane flying, or is that a whole different animal?

  3. My airplane also uses the green dot and has the same procedure for optimum relight speed. It's interesting to see that it follows the same logic as Airbus. Thanks for the info!

  4. I just passed my private pilot checkride today. I have that best glide speed imprinted in my brain.

  5. Wow. .82 mach. I had forgot there were airplanes out there that went that slow :)

  6. Thanks D.B. I too hope. But the great thing is to know that green dot is your friend. It's good to have friends that keep you out of trouble.

  7. Linda, This is a whole different animal. But... the small planes are so advanced, I wouldn't put it past them to have something like this. The plane you flew in... definitely not.

  8. Daniel, that's great! So now you can add that to your resume. That is very interesting. Thanks for the information.

  9. Pat... it's not how fast your plane flies but how it performs. Sometimes slower is better... or more efficient I should say.

  10. YEAH!!! SCOTE1992... YOU passed your checkride! Awesome. Way to go. Send me a picture and tell me about your ride.

  11. Just to clarify, are these green dot glide ratios at idle power, or charted engine out? I'm going to guess you're at idle power to get 28:1. The single engine folks might be thinking engine-out drift down.

  12. The glide ratio for then engine relight is a given...engines out. The green dot will always give you best lift to drag ratio... what that will be, we don't know. But the added info from the pilots... that has to be engine's at idle. Because, I'm guessing they're not out shutting down their engines to determine this. Thanks for the great question Pat.

  13. flight tsc236, an A330 has the gliding record in a comercial flight. In august 24th. 2001 glided for 75 miles, due to a complete fuel loss, to Azores Airport in the middle of the atlantic ocean. All 306 passengers and crew were saved thanks to Cpt. Robert Piché and FO. Dirk DeJager expertise.

    1. Best event ever... but they dumped all their fuel out and turned themselves into a glider. I suspect when you do that, you best be a glider pilot! Excellent flying skills


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