Hurricane Hunters

[PT20J]

NOAA has two WP-3D hurricane hunter aircraft that fly through the hurricanes to get real-time data. If you want to track them on FlightAware, they are registered as N42RF and N43RF.

EDIT: Looking at the track logs I noticed something interesting: When penetrating the storm, they hold the altitude steady and let the airspeed vary. I believe the optimum penetration speed is 210 kts and it varies pretty widely, but the ROC variation is minimal and the altitude only varies like +/-50 ft.

 

Edited September 29, 2022 by PT20J

[WAFI]

When they are flying missions you can take a look at the storm data. Pretty cool stuff...

https://www.tropicaltidbits.com/recon/

 

[A64Pilot]

3 hours ago, PT20J said:

NOAA has two WP-3D hurricane hunter aircraft that fly through the hurricanes to get real-time data. If you want to track them on FlightAware, they are registered as N42RF and N43RF.

EDIT: Looking at the track logs I noticed something interesting: When penetrating the storm, they hold the altitude steady and let the airspeed vary. I believe the optimum penetration speed is 210 kts and it varies pretty widely, but the ROC variation is minimal and the altitude only varies like +/-50 ft.

 

Must be due to data collection, if I ever get into bad turbulence I ask for a block altitude and hold airspeed and let her climb or descend

[hais]

5 hours ago, PT20J said:

NOAA has two WP-3D hurricane hunter aircraft that fly through the hurricanes to get real-time data. If you want to track them on FlightAware, they are registered as N42RF and N43RF.

EDIT: Looking at the track logs I noticed something interesting: When penetrating the storm, they hold the altitude steady and let the airspeed vary. I believe the optimum penetration speed is 210 kts and it varies pretty widely, but the ROC variation is minimal and the altitude only varies like +/-50 ft.

 

So that's the trick! Let me take out my Mooney and go try

[jaylw314]

5 hours ago, PT20J said:

NOAA has two WP-3D hurricane hunter aircraft that fly through the hurricanes to get real-time data. If you want to track them on FlightAware, they are registered as N42RF and N43RF.

EDIT: Looking at the track logs I noticed something interesting: When penetrating the storm, they hold the altitude steady and let the airspeed vary. I believe the optimum penetration speed is 210 kts and it varies pretty widely, but the ROC variation is minimal and the altitude only varies like +/-50 ft.

 

Does ADS-B altitude data use GPS altitude or the aircraft's encoder altitude?

[GeeBee]

I've always wanted to fly that mission. I had a co-pilot who flew those missions in a C-130 and he really enjoyed the challenge. You have to fly constant altitude to get good pressure gradients by the way. 

There is one on "Air Disasters". 5.5 g's plus #4 on fire. Also not mentioned, #3 was flapping a prop boot.

 

https://weather.com/storms/hurricane/news/hurricane-hunter-turbulent-flight-patricia-irene-hugo

[N201MKTurbo]

I was watching the weather planes fly in the hurricane. The ones I saw were using the call signs TEAL73 and TEAL71. You can look them up on FlightAware. They were flying out of Louisiana. I watched one go from a ground speed of 350 KTS. To 73 KTS in 30 seconds. Now that’s wind shear. 

[MB65E]

Also named Ms.Piggy and Kermit D Frog respectively!

I hangared with them a few years for the McDill airshow. Such amazing talent in those hangar. Mr. Greg Bass was the lead pilot at the time with something like 300 eye wall penetrations. Awesome stuff. They apply Proseal to the leading edges up to 1/2 thick to help with erosion. 

Ran into a crew in Hawaii running the NOAA GiV they had significant Equiptment on that airplane too!! These guys made the USAF look like a training Sq! 
-Matt

[Pinecone]

I will have to talk to a friend of mine.

She flew WC-130s out of Guam in the early 80s.

Interesting lady, she flew for NASA after getting out of the USAF.  She was one of the main pilots for the Vomit Comet, doing Zero G rides.

[A64Pilot]

On 9/29/2022 at 7:45 PM, jaylw314 said:

Does ADS-B altitude data use GPS altitude or the aircraft's encoder altitude?

I believe the encoder, GPS altitude isn’t always that accurate, years ago I flew with Flight Prep EFB and one of the things it had was highway in the sky, which was a series of boxes that if you flew from one box to the other you were on course, usually if you were on altitude you were flying above or below the boxes due to GPS altitude inaccuracies.

‘I’ve read that GPS uses a flat Earth model for altitude, and of course the Earth isn’t round, better description, but bottom line never fly GPS altitude.

http://gpsinformation.net/main/altitude.htm

[0TreeLemur]

On 10/1/2022 at 9:12 AM, A64Pilot said:

I believe the encoder, GPS altitude isn’t always that accurate, years ago I flew with Flight Prep EFB and one of the things it had was highway in the sky, which was a series of boxes that if you flew from one box to the other you were on course, usually if you were on altitude you were flying above or below the boxes due to GPS altitude inaccuracies.

‘I’ve read that GPS uses a flat Earth model for altitude, and of course the Earth isn’t round, better description, but bottom line never fly GPS altitude.

http://gpsinformation.net/main/altitude.htm

"Flat Earth Model"?  There is no such thing.  Are you trying to be funny?    Not obvious if so.

The web page you cite is ancient by GPS standards, written waaaay back in 2001.  Before WAAS.

Anyhow, the design of the GPS system uses the WGS84 Datum, which pretty accurately defines the shape of our planet as an oblate spheroid, with something like a 20 km greater radius at the equator than at the poles.

Vertical position errors tend to be larger than horizontal errors because of satellite geometry.  The apparent velocity of the GPS satellites is faster when directly overhead, so that most satellites used to calculate the position solution are nearer the horizon than the vertical- they spend more time near the horizon than overhead.  Small signal timing errors due to atmospheric effects on signal propagation contribute a larger component in the vertical direction when the satellite is nearer the horizon.  The WAAS system provides receivers with an error model to minimize these random propagation errors and their impact on the horizontal and vertical position estimates.

A contemporary reference: https://sage-answer.com/what-datum-is-used-by-gps/

A WAAS GPS system reports the expected vertical error.   If the system is working correctly, it's less than 2 m.   Because signal availability is not guaranteed, and to avoid problems with equipment failures, we use encoders.

[Pinecone]

4 hours ago, 0TreeLemur said:

Anyhow, the design of the GPS system uses the WGS84 Datum, which pretty accurately defines the shape of our planet as an oblate spheroid, with something like a 20 km greater radius at the equator than at the poles.

Funny thing is, the WGS84 Datum does not have 0 degrees longitude correct.

I took a portable GPS to Greenwich UK and placed it ON the Prime Meridian.  And the GPS said it was off by almost 100 yards.  The GPS places it out in the parking lot.

[GeeBee]

The prime Meridian in Greenwich is not WGS 84 measurement. It is not a matter of "correct"  it is a matter of the datum being used consistently. As long as you use the same datum to mark places and use that datum in navigational measurement it is all correct.....for that datum.  Think of it as using different base numbers to describe a numerical amount.  I bet if you change the datum to OSGB36 your GPS would be close if not spot on. Nor is a datum perfect for each region of the world. Interestingly in the Bahamas if you use the 1816 datum which used sticks and chains, it is most accurate datum....in that area but things shift quickly by the time you get to the Turks. WGS 84 represents some compromises in some places, but by using it everything can be described accurately even if the surveyors chains do not count off the correct amount because of GPS. No longer do you count chain links, you count time and mark the point accordingly using the GPS 84 datum.

http://www.thegreenwichmeridian.org/tgm/articles.php?article=7

[0TreeLemur]

2 hours ago, GeeBee said:

The prime Meridian in Greenwich is not WGS 84 measurement. It is not a matter of "correct"  it is a matter of the datum being used consistently. As long as you use the same datum to mark places and use that datum in navigational measurement it is all correct.....for that datum.  Think of it as using different base numbers to describe a numerical amount.  I bet if you change the datum to OSGB36 your GPS would be close if not spot on. Nor is a datum perfect for each region of the world. Interestingly in the Bahamas if you use the 1816 datum which used sticks and chains, it is most accurate datum....in that area but things shift quickly by the time you get to the Turks. WGS 84 represents some compromises in some places, but by using it everything can be described accurately even if the surveyors chains do not count off the correct amount because of GPS. No longer do you count chain links, you count time and mark the point accordingly using the GPS 84 datum.

http://www.thegreenwichmeridian.org/tgm/articles.php?article=7

Did that too when I visited Greenwich.   Datum, spheroid, coordinate systems are all approximations.   Also, since 1984 the Greenwich observatory has moved about 40 cm east.  Just wait until the new coordinate reference system comes out in a few years....

[Pinecone]

10 hours ago, GeeBee said:

The prime Meridian in Greenwich is not WGS 84 measurement. It is not a matter of "correct"  it is a matter of the datum being used consistently. As long as you use the same datum to mark places and use that datum in navigational measurement it is all correct.....for that datum.  Think of it as using different base numbers to describe a numerical amount.  I bet if you change the datum to OSGB36 your GPS would be close if not spot on. Nor is a datum perfect for each region of the world. Interestingly in the Bahamas if you use the 1816 datum which used sticks and chains, it is most accurate datum....in that area but things shift quickly by the time you get to the Turks. WGS 84 represents some compromises in some places, but by using it everything can be described accurately even if the surveyors chains do not count off the correct amount because of GPS. No longer do you count chain links, you count time and mark the point accordingly using the GPS 84 datum.

http://www.thegreenwichmeridian.org/tgm/articles.php?article=7

 

No, the point is, the Prime Meridian is the Prime Meridian.  It is a physical point.

Yes, GPS works because it is consistent.  It will take you back to the exact same point. 

BUT, if you put in a lat/long it doesn't take you to that point exactly.

OTOH, many places were not exactly where we thought they were.  Early uses of INS discovered this.

[Pinecone]

7 hours ago, 0TreeLemur said:

Did that too when I visited Greenwich.   Datum, spheroid, coordinate systems are all approximations.   Also, since 1984 the Greenwich observatory has moved about 40 cm east.  Just wait until the new coordinate reference system comes out in a few years....

Yeah, and there were a few others doing the same thing.  Amazing how many geeks there are in the world.

 

[GeeBee]

4 minutes ago, Pinecone said:

 

No, the point is, the Prime Meridian is the Prime Meridian.  It is a physical point.

Yes, GPS works because it is consistent.  It will take you back to the exact same point. 

BUT, if you put in a lat/long it doesn't take you to that point exactly.

OTOH, many places were not exactly where we thought they were.  Early uses of INS discovered this.

The Prime median in Greenwich is a historical physical point. Historical being the operative word.

[Pinecone]

But is it not the prime meridian by definition?

If not, where is the actual 0 longitude?