High Speed with Tailwind
Dec 21, 2016 | 10:01 am
#31
Suspended
Join Date: Nov 2015
Posts: 1,808
On UA 1279 IAH to BOS on 12/16 (B739), with blustery weather in the Northeastern US the Flight Map indicated that our speed at one point hit 686 mph. I was hoping to break 700 mph, but I could feel the engines reduced when we were in the 680 range. After deplaning, I waited for the pilots to ask a question. I approached a person in pilot's uniform and he said that he did not fly the plane (I assume he was non-rev?), but that the day before he flew the route and had a tailwind of 168 mph. Rather than waiting for this flight's pilots (who seemed to be waiting for all passengers to get off), I moved on to catch my ride. I started thinking, what was the maximum speed observed by other FT'ers on a commercial (Non-Concorde/SST) flight?
When flying into a headwind, the airspeed can be very high, but the groundspeed much lower. There is lots of air passing quickly over the wings, but the headwind offers resistence and reduces the speed at which you are going over the ground.
In a tailwind, the airspeed can be low but the groundspeed can be very very high.
Airspeed/groundspeed can be thought of like a fish swimming in a bowl. The fish may be going 2mph from one end of the bowl to the other..but if the bowl is on a train going 40mph, the fish has a 42mph groundspeed. Fast fish!!
There is even a strange phenomena that is sometimes seen with smaller aircraft where the airspeed reduces groundspeed to 0. If you are going 80mph into and 80mph headwind, the aircraft will still fly but remain still..like it's hovering. There is enough airspeed to keep the aircraft flying, but no groundspeed.
Anyhow, it did not happen to me but to my sister several years ago. She was eastbound, from PHX to YYZ and I was watching the flight on flightaware. Somewhere around ORD there was a 170mph tailwind and the Airbus's groundspeed was pushing 700. She said the flight was amazingly short for that distance. Of course, people going westbound had the opposite effect and had very very low groundspeeds, making their flight longer.
Dec 21, 2016 | 10:55 am
#32
FlyerTalk Evangelist
Join Date: May 2002
Location: Pittsburgh
Programs: MR LT Titanium, AA LT PLT, UA SLV, Avis PreferredPlus, HH Gold, Hertz PC, National Executive, etc.
Posts: 31,670
And if we're working on clarifications, in no situation are any of these "supersonic". A plane may be traveling relative to the ground at a speed faster than the speed of sound through still air at the surface. But "supersonic" flight refers to the relative speed of the aircraft through the surrounding air, as a frame of reference. Commercial aircraft are not designed to travel supersonic.
Dec 21, 2016 | 6:15 pm
#33
FlyerTalk Evangelist
Join Date: Jun 2005
Posts: 38,543
for every tail, there is a head wind. we once had to stop in iceland to gas up on a muc-iad flight. very cold, and lots of wind. we got dumped on the tarmac in the dark, and were told not to let go of the rope(ran from plane to airport)
bought lots of iclandic wool sweaters
came back recently from lhr to iAd. we dropped south of england, and did not take great circle route. head winds were under 10 knts.
bought lots of iclandic wool sweaters
came back recently from lhr to iAd. we dropped south of england, and did not take great circle route. head winds were under 10 knts.