Question about Airspeed vs Groundspeed

Laden, or unladen?

a reply to: Bedlam

African or European?

Well, you could bear the coconut on lines held under the dorsal guiding feathers...

a reply to: Bedlam

They could work together.

a reply to: Zaphod58

I cannot disagree with that fact. I'm also proud of having a ground speed over 200 knots.

originally posted by: Bedlam
Laden, or unladen?

Bin Laden.

originally posted by: RogueWave
a reply to: 727Sky

At 37,000+ feet I may be only indicating 200 knots or even 220 but my true airspeed can be 440 or 460 knots across the ground under no wind.

Do you mean this difference is explained by backwind?

No. Wind has no effect on True airspeed. A discussion of airspeed begins with Indicated Airspeed, which is merely a reflection of the amount of air entering the pitot-static system through the opening in the pitot tube, which is normally pointed more or less straight ahead with reference to the longitudinal axis of the aircraft. Sometimes the position of the pitot tube can affect the amount of air going in because of, for example, venturi effect near the pitot location, so the aircraft manual gives a correction to arrive at Calibrated Airspeed. Since the airspeed indicator measures the mass of air going in the pitot, anything that affects that mass, like density,must be corrected for. So, you must correct for pressure and temperature. In practice, temp and pressure are most closely related to altitude, so pilots use either a preprogrammed calculator or a slide rule sort of thing called an E6B or C-12, where you put in indicated or calibrated airspeed and pressure altitude and sometimes temperature, and it gives you the True Airspeed. In modern jets the aircraft flight computer figures it for you. It gets more complicated when you get into the transonic and supersonic regions where you have to figure in compressibility and the like.

a reply to: F4guy

True Airspeed. In modern jets the aircraft flight computer figures it for you.

So would this be the airspeed that would be recorded on the FDR?

Hello,
I'm new to this as of today. I have a
question regarding whatever hit the
pentagon. If a plane was traveling 500 MPH
at what point in its decent would it need to
be at the 15 feet it was above ground and
for how long? It seems as if this thing would
have needed to be hovering for quite some
distance in order to impact the pentagon
in the way the video shows. At this speed 700 plus feet per second what else besides
a few light poles did this thing encounter.
To be open & honest I obviously have no
idea what hit the pentagon but I will say I
can't believe it was a huge airliner. To be able to decend at 500 MPH effectively and put yourself at an impact zone which looks to be dead-on straight and not much higher than 10-15 feet off the ground seems incomprehensible to me and so far from possible it's astonishing. The greatest pilot
on this planet can't defy odds like this even
if the physics were possible let alone a few
guys that were trained in a simulator.
The fact that this story holds its ground to
this day without tremendous confrontation
is also astonishing too me. If someone can
help me better understand that would be
great.

a reply to: RogueWave

That is up to the designer of the FDR. As elaborate as computers are today, they can record many parameters. I guess it depends on how many sensors they want to mount.

From a skydiving perspective groundspeed is the speed of the canopy's flight plus/minus wind speed, depending on if you're going downwind or with the wind.

a reply to: Hellothere7

Well Hellothere! (Sorry, couldn't resist it.)

Welcome to the boards! If you have any questions about ATS, feel free to send me a u2u and I'll be glad to help you out.

Or you can swing on by the ATS Freshman's Forum and learn aplenty! Following that, don't forget to Introduce yourself. Not only is a great way to meet some like-minded individuals, but a great way to start some awesome dialog with different-minded folks.

This thread really isn't the proper venue for the greater 9/11 Conspiracies, however we do have an entire forum dedicated to 9/11 Conspiracies. I do have one thing to say in response to your post though: Everyone said that when Captain Sully landed US Airways Flight 1549 in the Hudson River with no loss of life it was defying the odds and physics.

And again, welcome!

How about the Air Canada crew that dead sticked a 767.

originally posted by: RogueWave
a reply to: F4guy

True Airspeed. In modern jets the aircraft flight computer figures it for you.

So would this be the airspeed that would be recorded on the FDR?

I dislike this answer as much as you will, but....It depends. There are myriad models of FDRs, made by a number of different manufacturers like L3 and Sundstrand and others and they record a number of parameters from 18 to over 1000. At a minimum indicated airspeed is sensed and recorded. To determine exactly what parameters are recorded you have to look at the Type Certificate Data Sheet for the particular aircraft. If you give me the aircraft model and serial number and a couple of days, I can look it up, but for now, I just got back from Doha and my Knob Creek is waiting.

a reply to: F4guy

Boeing 777-200ER.

Enjoy!

a reply to: JIMC5499

Indeed!

And in both cases, the laws of physics were not defied, they were complied with. Energy management, and good fortune.

a reply to: RogueWave

I would also need the serial number because different end users order different configurations and different data configurations. For example there are differences in what is kept in non-volatile memory in different inertial nav systems. And the 777 came with either General Electric GE90, Pratt & Whitney PW4000, or Rolls-Royce Trent 800 engines. In addition to looking at the TCDS, it is necessary to look at the build sheet for the particular serial number. That would show if an L3 FA2100 Solid State Flight Data Recorder or analternative from Allied Signal or one of the other DFDR manufacturers was used. And almost all, but not absolutely all 777s have a digital data bus and/or a digital flight data acquisition unit. Are you sorry you asked yet.

so in a piper j-3, we fly backwards over the field sometimes...in spring specially
.
so, can an airplane stall if it's encountering a change in wind direction....by 35 miles an hour?
Oh yes, due to the inertia of the aircraft.

a reply to: F4guy

Are you sorry you asked yet.

No, not at all.

Allied Signal Model
Number 980-4700-003
Serial Number 2196


Rolls Royce engines.


Serial nr of plane is 28411.

a reply to: RogueWave

This SFDR (Solid State Flight Data Recorder) captures indicated airspeed, but since it also records pressure altitude, true airspeed can be calculated. BTW, I assume you're interested because that serial number is the Malaysian 777 shot down over the Ukraine.