Freshlove1 From , joined Dec 1969, posts, RR: Reply 3, posted (9 years 10 months 3 weeks 1 day 17 hours ago) and read 6875 times:
the 737-200 with a weight if 50,000kg and 5% of flaps would have a V1 speed of 131 according to what I found on google, the 747 is 148kts for general speed depending on what series you are looking for, all of this can be found on google. hope this helps
COIAH99 From United States of America, joined Dec 2003, 251 posts, RR: 5 Reply 4, posted (9 years 10 months 3 weeks 1 day 17 hours ago) and read 6854 times:
How I understand it...The V speeds are different every time. Depending on wind, temp., weight of a/c etc. I'm not a pilot but from doing weight and balance the V's speeds are a variable number. Any pilots out there please correct me if I'm wrong.
To answer you question there might be a specific range for each a/c model but I could not tell you what they are.
Mir From United States of America, joined Jan 2004, 20484 posts, RR: 56 Reply 5, posted (9 years 10 months 3 weeks 1 day 13 hours ago) and read 6772 times:
Well, V1 is not really a takeoff speed. V1 is the go/no-go decision point, calculated so that once that speed is reached, there is not enough runway left to stop the plane, so even if there is an engine failure, the pilots will lift it off the runway. VR is the rotation speed, and that's when the pilots start pulling back.
It does vary on a number of different things, including weight, temperature, humidity, altitude, flap setting, etc. V1 is also very dependent on the length of the runway.
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Kilavoud From , joined Dec 1969, posts, RR: Reply 8, posted (9 years 10 months 3 weeks 1 day 6 hours ago) and read 6551 times:
I would like very much to know what is the speed of a 747-400 fully loaded for a 13 hours flight, just before taking off ? And is that speed different for a fully loaded 747-400 departing for a 9 hours flight ?
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 69 Reply 12, posted (9 years 10 months 2 weeks 6 days 23 hours ago) and read 6209 times:
The primary variables for V1, VR and V2, are slat/flap configuration and gross weight.
In non-normal conditions such as contaminated runway or hot/high airports there may be adjustments on the order of 3-5 knots for V1 and VR but probably not for V2 which is an in-flight indicated airspeed and not dependent on winds or runway slope, condition etc.
V1 may actually be reduced twenty knots or more for takeoff on runways with braking action less than good.
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411A From United States of America, joined Nov 2001, 1826 posts, RR: 9 Reply 13, posted (9 years 10 months 2 weeks 6 days 20 hours ago) and read 6168 times:
SlamClick is generally correct with regard to turbojet/turbofan powered aircraft (ie: V2 is an airbourne speed, and varies with weight and configuration only) however, with many turbopropeller powered, and all piston powered transport aircraft, V2 is achieved before rotation, by regulatory requirements.
Jetguy From , joined Dec 1969, posts, RR: Reply 14, posted (9 years 10 months 2 weeks 6 days 20 hours ago) and read 6165 times:
Mir made the following quote: "...Well, V1 is not really a takeoff speed. V1 is the go/no-go decision point, calculated so that once that speed is reached, there is not enough runway left to stop the plane, so even if there is an engine failure, the pilots will lift it off the runway..."
Actually, V1 is very much a "takeoff speed" in as much as it's probably the most critical speed that a pilot has to determine in the takeoff sequence. As far as V1 being the "go/no-go" decision point - well, that's not quite correct either. Actually, V1 is the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
The point is that if V1 is the maximum speed in the takeoff at which the pilot must take the first action to stop the airplane within the accelerate-stop distance, then the decision to abort or continue the takeoff must be made at some point prior to reaching V1 (not at V1) in order to allow for pilot reaction time.
Buckfifty From Canada, joined Oct 2001, 1314 posts, RR: 20 Reply 15, posted (9 years 10 months 2 weeks 6 days 9 hours ago) and read 6091 times:
Though my understanding of V1 is that it is the speed when the decision to go or not to go is made. This 'decision' to go is to do nothing, but the 'decision' not to go is basically the first application of the brakes, combined with simultaneous retardation of the throttles and usage of the speed brakes (reverse thrust optional, but most likely used). The time between Vef and V1 is generally regarded as the 'recognition' phase (as in having just enough time to say ''oh shit''), not necessarily the decision making phase, though I can see your point too, Jetguy.
And as someone has alluded to above, V1 is highly dependent on Vmbe, Vmcg, and is more or less concerned with field length limited weight. But if you asked me, V1 is uber critical, but I would never think of it as a takeoff speed in a purist sense, as you're more worried about what runway is left rather than whether or not you can get up in the air. In that sense, if someone who is not an enthusiast or expert asks about at what speed an aircraft takes off at, I would refer to the Vr speed.
B747skipper From , joined Dec 1969, posts, RR: Reply 16, posted (9 years 10 months 2 weeks 3 days 5 hours ago) and read 5890 times:
If you wish to know the takeoff speed of a 747-200/300
at maximum gross weight of 377,800 kg (833,000 lbs), the
rotation speed ("VR") is 178 knots at sea level 15 degrees C.
Obviously the aurplane "leaves" the ground at about 180 kts.
It achieves its T/O safety speed V2, a few seconds later...
Happy contrails -
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 69 Reply 18, posted (9 years 10 months 1 week 3 days 6 hours ago) and read 5542 times:
That is only true in "balanced field length" takeoffs. And I don't think that in 25 years of flying jetliners I have ever made one of those. Most takeoffs are "unbalanced" and V1 may be reached thousands of feet from the end of the runway.
I assure you that the V-speed flip books that may be found in the cockpit of planes there was no entry point for runway length. I have consulted them thousands upon thousands of times. I have taught performance at two airlines for a total of over four years.
There is a whole description for establishing V1 speeds for an airplane in FAR Part 25. One of the many criteria is that runway length available must permit a rejected takeoff from that speed.
Again, the primary variables are flap/slat configuration and gross weight. There are often minor adjustments available for temperature and runways slope and for contamination.
Runway length is considered for "allowable takeoff gross weight" and the final weight will drive the V1 speed but that is the only relationship.
Happiness is not seeing another trite Ste. Maarten photo all week long.
Vikkyvik From United States of America, joined Jul 2003, 9017 posts, RR: 28 Reply 19, posted (9 years 10 months 1 week 3 days ago) and read 5482 times:
Question your last post brought to mind:
Let's say a jetliner is able to take off from a particular runway at max gross weight, and that at a certain power setting, V1 will be reached with plenty of runway to spare (hence an unbalanced takeoff). Would the crew then reduce takeoff power setting even further and use more runway space (for example, use a power such that in the case of an aborted takeoff at V1, the plane will come to a stop at or near the end of the runway), in order to save on engine wear and fuel consumption? Or is the power setting in this scenario more governed by the initial climb? Thanks for any replies.
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Kay From France, joined Mar 2002, 1884 posts, RR: 3 Reply 21, posted (9 years 10 months 1 week 2 days 9 hours ago) and read 5388 times:
There are facts in this thread I was not aware of. My understanding (and, if I may say from my readings here, that of several other A.net users) was as such:
I believed that the following factors:
- runway length
are fed into some kind of table/computer to determine what is the maximum speed at which the airplane can break heavily (without reversers, but with spoilers) and roll to a complete stop on the last inch of the runway.
That speed is called V1. However, Vr, which is the speed decided for rotation according to flap settings (which are in turn chosen according to runway length/weight/conditions), is usually greater than V1 in that it is the minimum speed needed for the airplane to lift-off. Logically, that speed is independent on V1, which is the maximum speed before having to stop on the available runway, V1 being largely dependent on the length of the runway and the ability of the airplane to accelerate at max and break at max.
I fully realize that what was stated in this thread (probably true), is in total contradiction! I am trying to get used to the fact that V1 is the minimum speed for the plane to lift-off on failure (how can that coincide with the max speed for stopping safely), and that V1 is dependent only on weight and flap/slap configuration.
In this new definition, V1 doesn't stand at all as the go-nogo speed, or at least not as we thought of it (there is enough distance to stop).
I am willing to forget about temperature and elevation used to determine V1, but runway length too? The purpose of V1 as we know it has been defeated!
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 69 Reply 22, posted (9 years 10 months 1 week 2 days 8 hours ago) and read 5388 times:
We might have misled you, or perhaps the combination of our statements here is confusing. I know it is to me.
Your understanding that V1 is "the minimum speed for the plane to lift off on failure . . ." is not correct. There is another speed, VMU or velocity-minimum unstick which is the lowest speed at which (under the given conditions) the plane can be pulled off the ground - with and without an engine failed. These demonstrations are done by the factory test pilots for the FAA and make for some very dramatic video.
No sir, V1 is the takeoff decision speed. The other descriptions of it are valid but functionally it is a speed we will reach during the takeoff roll before we rotate and lift off. "Decision speed" is a little misleading because the decision was already made before we start rolling.
The decision is: If we have a problem before reaching V1 we are going to reject the takeoff and keep our problem on the ground. If we have a problem after V1 we are going to continue the takeoff. And we are going to go flying no matter what the problem is because taking the plane around the traffic pattern for a more normal landing is less risky than attempting to stop it. For one thing we might not have sufficient runway/stopway to stop the plane without damage after V1.
Now, how do we get these speeds. Well they come off a table, often bound in a little spiral book, otherwise a large chart we can pull out of a pocket on the plane. We follow the instructions (we know them by heart after a few uses) and we get the proper speeds. OR: The come up on ACARS or a hard copy could be handed us when the door is closed. This version has correct speeds (and some other data) for this takeoff: Our actual weight/balance, the runway in use (its length and slope) the actual temperature and wind corrections as needed. Now these speeds might come from the same kind of chart we have in the cockpit but likely the computer generated them using the same algorithms that were used to build my hand-held V-speed chart, as supplied by the airplane's builder.
While looking for something else last night I ran across a V-Speed chart for Boeing 737 that is still in use at an airline where I used to teach (among other things) B-737 performance. Let's find one actual set of numbers off that chart for one specific condition:
On this chart, for each takeoff you would begin with the engine thrust rating to be used, 20,000 lbs for one side of the chart and 22,000 for the other. Conditions permitting, they may operate their 22K engines as 20K in a derated takeoff. So, we are going to use 22K or 22,000 lbs of thrust.
On the 22K side there is a small table I enter on the left side at the airport elevation. I go across to a point above the current (or assumed - in case of a reduced power takeoff) and since we are doing that I will go across to a point above 30oC and what I have is a graph of shaded and non-shaded areas, each marked by a letter. I find that this elevation and temperature puts me in area "C"
Next I make my flap selection. It offers me takeoff at flaps 5 or 15. We are going to use flaps 5 today. So I enter the Flaps 5 table at the top under column "C" which I got in the above paragraph. Column C will show me a column of V1, VR and V2 speeds.
Next I enter the same chart at the left side at my actual takeoff gross weight. Let's say we are at 135,000 lbs. On the 135K line I go across until I am in column "C" This box tells me that my speeds are to be:
V1 147 knots
VR 152 knots
V2 157 knots
Now there are two more small tables on this page. One gives me a reduction to V1 for a 2% down slope of the runway I may increase V1 by 3 knots if it slopes UP. This is because I can stop easier going uphill. I can delay the "decision" a little bit for this. It also says that I must reduce V1 by 3 knots if I have a 15 knot tailwind (longer stopping distance) or increase it 1 knot if I have a 40 knot headwind. Not likely to be using either of those.
The last table deals with VMCG which is only going to be a problem if my actual takeoff gross weight is less than 119,000 lbs. The inputs on this table are Actual outside air temperature and pressure altitude.
So, here are the numbers again.
V1 147 knots
VR 152 knots
V2 157 knots
And it will be these that we "bug" on the airspeed indicators and the non-flying pilot will call during the takeoff.
Hope that helps rather than just muddying the water further.
Happiness is not seeing another trite Ste. Maarten photo all week long.
Kay From France, joined Mar 2002, 1884 posts, RR: 3 Reply 23, posted (9 years 10 months 1 week 2 days 5 hours ago) and read 5363 times:
They come up on ACARS or a hard copy could be handed us when the door is closed. This version has correct speeds (and some other data) for this takeoff: Our actual weight/balance, the runway in use (its length and slope) the actual temperature and wind corrections as needed.
Runway length seems to be considered fully in this procedure. On the other hand, the description in the second part of your post about using charts on shaded-area tables etc, does not (more on this below).
For one thing we might not have sufficient runway/stopway to stop the plane without damage after V1.
I understand from this statement that runway length isn't the "primary worry" of having to use V1. It is one of the elements, a critical one, but not the primary.
Should that mean that runway length is, in some kind of way, considered more or less constant on all airports, and if an airport has a shorter runway (say 8 or 9,000 instead of 11,000ft), there is an additional "correction" to Vspeeds much like the ones that deal with runway slope, and tail/headwind described in the final part of your post?
That would make sense in a way that runways are long enough in many cases, and, runway length isn't the only factor that would make taking off (after V1) safer than trying to stop.
But that raises a question that, I guess, if I wanted to push it all the way, I would have to ask, even though it might appear a bit silly: is there a case where, when taking off from an infinitely-long runway (if that existed), if a problem occurred after V1 and before Vr, the crew might still deem it safer to take-off and make a pattern to land, rather than try to stop the plane there and then?
Because if there isn't, and V1 is still considered the take-off "decision" speed, then that would mean that runway-length was never intended to be a major factor in, well, V1!!!
I wish I could know the exact reason behind everything. But I discovered from my PPL that some matters have an impressive potential for complexity that make them impossible to learn "from distance"... At times, an "interpolate-under-uncertainty" approach imposes itself... which generates, in turn, corrections by specialists in the matter.
Very much appreciated corrections, I add. Thanks SlamClick for the detailed procedure for calculating V-speeds!!
BMAbound From Sweden, joined Nov 2003, 660 posts, RR: 4 Reply 24, posted (9 years 10 months 1 week 2 days 4 hours ago) and read 5347 times:
I was wondering about V1.
If a Lear has a V1 of, let's say 105 kts and a Vr of 115 kts and using a 15 000 ft runway, I know it can stop on the remaning distance if it encounters problems at 110 kts. My question is: Why is there a V1 if the runway is (well, in this case) 3 times longer than what the Lear actually needs?
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25 SlamClick: Kay I am just reading your post and I am not going to have time to do a line-item response but I want to set one thing straight before I shut down her
26 AAR90: My question is: Why is there a V1 if the runway is (well, in this case) 3 times longer than what the Lear actually needs? By definition, V1 will alway