Mjsmigel From United States of America, joined Oct 2002, 56 posts, RR: 0 Posted (12 years 11 months 5 days 21 hours ago) and read 3739 times:
Is it common for very high speeds to be used for takeoff/landing, simply because an airplane has a low gross weight and the runway is much longer than required?
I ask this because back in the late 1980s I reviewed some footage of aircraft taking off from DFW. I did some photogrammetry. Knowing exactly how many frames per second were in a "frame advance" on the VCR, and the fuselage length of that particular model, I used the speed = distance / time formula. I found some AA/DL MD-80 aircraft had reached 180-200 kt (error 10%) before they lifted off.
I assumed something was wrong in my computations until years later, when I discovered all this:
-- Depending on the aircrew, Key Airlines 727-100's I flew on from Tonopah Test Range into Nellis AFB 1989-90 sometimes flew highly unstabilized final approaches... I was on three flights where the pilot did an extremely short final, turning from base to final over the approach lights about 200 ft AGL.
It might be safe to assume that hot approaches/takeoffs are more common than we think.
On the other hand, the times that I used my GPS during takeoff/landing on Delta and Continental 727/737 flights in recent years, all speeds looked perfectly reasonable to me (110-140 kt).
I'm not trying to start a fire here or anything... this topic has always piqued my curiosity.
Pics of aircraft involved in hot approaches shown below for enjoyment...
B747skipper From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 11 months 5 days 20 hours ago) and read 3678 times:
Dear Mjsmigel -
I dont know if the 747 is the worst aircraft (being large and heavy) but here are the speeds applicable for a 747-200/300...
Takeoff maximum weight -
V2 speed (50 feet above runway) is 190 kts...
After flaps retraction we need V2+100 for maneuvers = 290 kts when climbing.
Landing maximum weight -
Vref speed 154 kts... we establish that speed no later than 500 feet AGL...
Add some 10 kts, maybe 15 knots for wind... rarely over 160 for landing.
Realize also that planes are not at maximum weights, meaning = slower...
Bellerophon From United Kingdom, joined May 2002, 586 posts, RR: 58
Reply 3, posted (12 years 11 months 5 days 14 hours ago) and read 3375 times:
Remember that what you have calculated from your film (and also what the readout on your GPS showed) is the aircraft groundspeed (GS). What the pilot was using was indicated airspeed (IAS), and you would need to know what the wind at take-off was to deduce the IAS.
It is possible there was a tail wind component on the take-offs you looked at, which would mean the GS was higher than the IAS.
Most airline operators instruct their pilots fly the scheduled speeds, and most lay down a point by which an approach must be stabilised. In the event of an incident, the Flight Data Recorder will show exactly how the aircraft was being flown, and any deliberate breach of company procedures it reveals is unlikely to be treated with much sympathy.
If you have calculated your take-off and approach speeds correctly, in accordance with the Aircraft Flight Manual, using the prevailing atmospheric conditions, then there is nothing to be gained by arbitrarily increasing those speeds. In my experience, the vast majority of airline pilots fly by the numbers.
For my aircraft type, at maximum weights, typical speeds are:
Initial Climb Out.....250 kts
Approach..............192 kts.........down to 800R
Landing................169 kts...stabilised by 500R
ThirtyEcho From United States of America, joined Dec 2001, 1710 posts, RR: 1
Reply 4, posted (12 years 11 months 5 days 8 hours ago) and read 3304 times:
Remember that taking off into the wind means that the GS will be lower than the IAS; all that your system of speed estimation produces is a GS reading, even if it is accurate. If an aircraft rotates at 150KIAS, but is flying directly into a 20KT headwind, its groundspeed is only 130KTS.
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 1
Reply 5, posted (12 years 11 months 4 days 23 hours ago) and read 3225 times:
To add to what ThirtyEcho said- the temperature may have been quite high also which would have meant that the TAS and therefore the GS would have been quite high by the time you reach VR IAS. High temps=High TAS for the same IAS
OPNLguy From , joined Dec 1969, posts, RR:
Reply 8, posted (12 years 11 months 4 days 1 hour ago) and read 3088 times:
>>>-- Continental DC-9 at IAH in 1996, too hot (200+ kt) on the final approach and rolled off the runway.
Well, yes, they were indeed fast, but it wasn't a "normal" approach by any stretch of the imagination. If you'll look at the NTSB stuff you linked, you'll note that they didn't have hydraulic pressure available to actually extend the landing gear and flaps because of a human error. That error initiated the accident chain, and the excessive speed was a consequence of that error, and not the error itself...