View Full Version : Training and use of airborne weather radar


tubby linton
6th Jun 2009, 22:30
I remember reading an article in Aviation International News about a study made by one of the weather radar manufacturers into the training given to airline pilots in the use of airborne weather radar.
The study basically concluded that the training given was very poor ,and most pilots had a very poor understanding of how to use their weather radars effectively or that the returns on the display could mean different things if the gain was moved out of calibrated setting.
What training in your radar have you received and what settings do you use and does anybody have a link to the original study?



tubby linton
7th Jun 2009, 10:40
The report findings are reproduced here:

Honeywell Aerospace Pilot Survey Findings
By: Ian Goold

Aviation International News >> May 2008
Training

In conducting a survey about the RDR-4000 weather radar, Honeywell safety specialist Dr. Ratan Khatwa asked more than 50 ATP-rated pilots about their experience with weather radar. The average age of the respondents was 52 years; the average flight time was 12,500 hours. The answers these experienced pilots provided were illuminating.

• 62 percent of the pilots surveyed answered correctly that a straight radar beam is not aligned with an aircraft’s current flight level (because of Earth curvature)

• 15 percent mistakenly thought that antenna down-tilt was required to offset a nose-up pitch angle. (That is offset by antenna stabilization.)

• 63 percent did not appreciate the need for weather-radar antennas to be set to compensate for earth curvature, which blocks weather targets beyond, say, 150 nm ahead for nominal cruise altitudes. “Curvature [effects] become noticeable at ranges above 40 nm, and if ignored can lead to weather-image interpretation errors,” said Khatwa.

• 55 percent of pilots did not realize that a weather target falling inside the radar beam will not necessarily be shown in its true color on the display. “The color selected for display is a direct function of the power returned to the receiver. Where the beam is partially filled, the total power returned may not represent the calibrated value associated with the target cell,” he said.

• Five in every eight pilots incorrectly thought green (short-range) radar targets shown near to cruise levels above FL310 need not be avoided. “Typically, at these altitudes, targets are less reflective. At high altitudes, there is a possibility of unstable air and hail above the storm cell. It is therefore not advisable to penetrate the less-reflective part of the storm top,” Khatwa explained.

• 73 percent of flight crew understood that antenna tilt angle does not need to match a climb (or descent) angle to detect weather on their flight path. “The antenna should be pointed at the base of convective weather during climb. Generally, the lower 18,000 feet is the most reflective part of the storm.” Radar can be used to analyze weather characteristics (such as vertical extent of cells) and to avoid strong convective activity. “Returns along the flight-path angle may not provide full indication of storm intensity and turbulence levels [to be encountered within the cell].”

• Almost 90 percent of pilots did not know the range at which their current weather radar was no longer calibrated and did not show returns at their true levels. Radar beams broaden with distance, so a smaller proportion is filled with moisture. “At shorter ranges, returned power is more representative of the target cell, and it is more likely to be displayed at its true calibrated value. Typically, returns are calibrated within a range of 60 to 80 nm.”

avspook
7th Jun 2009, 10:48
Trained repair engineers and AME in operation & Maintenance of WXR.
In 25 Years I have never had crew allocated bye either airlines or defense forces. There IS a Gap.

falconer1
7th Jun 2009, 11:17
for opening up THAT CAN OF WORMS..

albeit knowing about the inherent design limits of airborne weather radar for tactical weather avoidance this could become a long overdue and highly interesting and educational thread...

roljoe
7th Jun 2009, 11:17
Hi,

this file is verry interesting, and anyway will enrich your understanding of the system.SmartCockpit - Airline training guides, Aviation, Operations, Safety (http://www.smartcockpit.com/pdf/flightops/aircraft/1)

rgds

Dream Land
7th Jun 2009, 11:19
Wow, I'm impressed at all that technical knowledge but some of us just had to figure it all out on their own using several types of wx radar, I really have no idea how to measure the height of a CB, but I do have a pretty good idea about how to keep an airplane out of the bad stuff.

Deficiencies that I see on the line is not keeping an eye outside the windscreen at the appropriate time, people trying to deviate around planet Earth, and knowing a bit about shapes of returns associated with convective weather.

foresight
7th Jun 2009, 11:52
training given was very poor

I think non-existent might be a better description.

i have been amazed by the ignorance of WX radar operation I have come across. Sometimes it is just set the range at 160, tilt at 0 (!) and gain in auto and then never touch it! No ideas about evaluating targets by changing settings. Not infrequently I have set the radar as I like only to find a sneaky hand has put it back in the above default position.

Having spent my early career in heavy turboprops (at horrible flight levels) in the tropics, I learnt the hard way and by seeking out information. I learnt a lot from experienced captains but nobody ever formally taught me anything.

In European short haul operations it is not so common to meet wall to wall CB activity so maybe it is way down the list of priorities. Hopefully, whatever the ultimate cause of the AF crash, the discussion of weather it has initiated will make the right people sit up and take notice.

JABBARA
7th Jun 2009, 12:06
At different times, I downloaded or acquired a total of more than 2000 pages about the usage of airborne weather radar. And almost 70% of those, I read and understand them throughly. Sometimes they were repeating each other or sometimes they were pointing out a different part of subject. But they were never contradicting.

In my line life of 25 years, I see 95% percent of my collagues are unaware of the correct use of wx radar (mainly tilt). Among them there were very experienced pilots. After some age, it is diffucult to convince them the correct way and kill the old habits of those which heritaged from old-style green painting radars.

At the end, I am not surprised with the result of survey mentioned by TL.

Regards.

Wing Root
7th Jun 2009, 13:59
Archie Trammell is considered a bit of a guru when it comes to WX radar. This PPRuNe thread contains an entire article of his from a 1987 issue of Business and Commercial Aviation and makes for interesting reading.

Terminal Area Weather Radar Technique (http://www.pprune.org/tech-log/48016-terminal-area-weather-radar-technique.html#post440714)

Also a video of his makes for very interesing viewing - if you can find it.

misd-agin
7th Jun 2009, 17:33
tubby linton -


• Five in every eight pilots incorrectly thought green (short-range) radar targets shown near to cruise levels above FL310 need not be avoided. “Typically, at these altitudes, targets are less reflective. At high altitudes, there is a possibility of unstable air and hail above the storm cell. It is therefore not advisable to penetrate the less-reflective part of the storm top,” Khatwa explained.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

It's been my observation, and the observation of most of my coworkers, that the majority of us flying tropical weather do not leave the radars in the calibrated gain settings. The only way to see the "less-reflective part of the storm top" is to get out of the calibrated gain setting.

tubby linton
7th Jun 2009, 20:23
Doctor Khatwa made his comments in two presentations ,one n 2007,the other in 2008.The presentations were at European conferences organised by the flight safety foundation.Unfortunately the original documents seem very difficult to access
I agree with him in his assertion that radar training is poor.How many of you know what the calibrated range of your weather radar is?

Jaun Huw Nose
7th Jun 2009, 21:26
Tubby you're right, I think I own one of the only copies of the Collins wx radar pilots manuals in the company and I've asked for wx radar to be covered in refresher training but it never has been.:ugh: Propilot magazine had a couple of good articles about it recently.

Graybeard
8th Jun 2009, 14:52
Color vs. intensity of return is calibrated up to 100 miles out in radars produced since about 1982. It may be less for some models radar; it certainly is for planes with smaller than airline standard 29 inch antenna plate. This is known as STC, Sensitivity Time Control, range. Beyond that, the radar kind of guesses at actual intensity. The farther out a return is detected, the more likely it will display red. Within the STC range, the color/return is calibrated.

Increasing the gain from CAL is effective only within STC range, as the receiver gain is already at max for returns greater than 100 miles.

What has been the experience with the newer Collins and Honeywell radars with automatic tilt and gain?

GB

Denti
8th Jun 2009, 15:29
The report cited in #2 seems to be true from my personal experience although that is allways anecdotal evidence only. However you have to keep in mind that it is also a report used to promote the first member of Honeywells Intuvue 3D weather-radar family (RDR-4000) which basicly promises to do nearly everything on its own and automaticly. Judging from the product webpage it can indeed provide quite a lot of help to the average pilot, especially if that pilot received the cited bad training.

Would love to hear from someone that uses it how it works in the real world, apparently it is in use on the A380 and will be in use on A350 and Gulfstram 650.

tubby linton
8th Jun 2009, 15:47
MyFCOM VOL1 states that the gain adjusts receiver sensitivity to enhance ground mapping in MAP mode only.
In FCOM Vol 2 it states that gain should always be left in automatic,unless specific display enhancement is deemed necessary.
The majority of my colleagues use manual gain outside the terminal area as the radar appears to understate the weather.
I am currently looking for the make and model number of my aircraft's radar so that I can try an find a copy of the manufacturers handbook for it but I have never received any radar specific training.

falconer1
11th Jun 2009, 20:29
safetypee ( in the A330 Tech Thread) correctly reminds us all of some severe stuff that had happened years ago, when a commuter a/c manufacturer changed the radar spec from an older high powered cloud slicer to their suppliers new (ever so top top top whatsoever) low powered digital flashlight radar..

make no mistake, that EFIS cockpit looked the same as the older birds..

BUT somebody forgot to inform the crews..

so they were looking at the same radar picture on their MFDs and EHSIs..

the radar had the same controls, in short you wouldn't have been able to tell the difference in the radar by looking at the cockpit..

only to find, well, all of a sudden, two different, highly experienced crews, who never dented a bird before, had hail damage on two different planes of the newer types..within a week of putting the new birds into service..

same clouds, same location, all the same..

EXCEPT, the new radars "led" them directly into the thick of some cells..

well, one should add, that the radar manufacturer also had forgotten to tell the aircraft manufacturer that their old radome spec wouldn't be good enough anymore...(well they had not forgotten, it was written in the installation manuals.., but alas, nobody at the aircraft manufacturer cared to read... sort of had overlooked the small print in the installation manuals..)

anyway, nobody got hurt, the insurance paid for the hail damage on the birds..

but coudda been worse...

ZFT
12th Jun 2009, 02:00
From the training perspective I am somewhat surprised at the apparent poor training comments when modern simulators have the ability to simulate extensive environmental conditions with the associated radar and visual simulations.

Is the apparent poor training being received due to deficiencies within the training programs or are the weather and radar simulations inadequate to provide the level of fidelity required?

falconer1
13th Jun 2009, 21:19
we would need a dedicated simulations engineer to answer your question..

or are the weather and radar simulations inadequate to provide the level of fidelity required? personally never have seen any "good" WX simulations..

and it is a very valid question you pose, though by the nature of things I would think that it is simply impossible to simulate a true WX condition, "true" meaning that all the unknowns of a dynamic target and the reaction of a specific WX radar / airframe / avionics combination could be put into a simulation model..

maybe its possible but I doubt it..

all other stuff you can simulate pretty well by now, but WX targets, probably would need a quantum computer just to calculate all possibilities..

and then you still would not know, whether the crews interpretation of the WX image could be transferred to the real world..whether you would have a hit or a miss in reality..too complex, too many factors involved..

how do you want to simulate attenuation and its associated problems in the sim???

vapilot2004
13th Jun 2009, 23:16
Back in the old days of analogue radar, more attention was paid to finessing the thing and using several settings and subsequent screen paints to interpret the returns. Intensity, tilt, range and sensitivity were all put to good use.

Digital radars are treated more like mysterious boxes in training with little insight offered into their internal workings. This unshared insight has the potential of unlocking the finer points of use, particularly when operating at the limits of the units performance.

Across the board, system concepts and theories used to be covered in depth. Unfortunately with today's highly automated aircraft, the dumbing down philosophy marches on.

wonwinlow
13th Jun 2009, 23:26
This is a copy and paste from the latest Rockwell Collins WXR-2100 Multiscan Radar manual equipped in my fleet which begs you to leave it in fully auto gain.


"The top of a thunderstorm is composed entirely of ice crystals (glaciated) and reflects very little radar energy. At temperatures less than –40 oC, liquid water no longer exists and only ice crystals are present. The altitude at which this temperature occurs varies depending on the time of day, time of year and based on latitude and longitude. Ice crystals are formed when the positive hydrogen atoms and the negative oxygen atom of water molecules lock or freeze the molecules into an ice crystal lattice. Ice crystal molecules are not able to change orientation to respond to and reflect radar energy. The middle portion of a thunderstorm occurs above the freezing level (0o C) and up to the altitude where the outside air temperature drops below –40oC. This section of the storm is composed of a combination of ice crystals and super cooled water. The super cooled water provides moderate reflectivity, but some reflective energy will be lost due to the presence of ice crystals. The top of this section of the storm is often referred to as the wet top or radar top of the thunderstorm. Building thunderstorms also have a turbulence bow wave that extends well above the visible top of the thunderstorm. The bow wave may cause severe turbulence but is completely invisible to radar."

Having read that, I found myself avoiding cells that are sometimes 4 to 5000 feet below me or cells that are not even there...so guess what? ...2 clicks out of auto gain and you really have the correct picture on the nav display, but I leave the F/Os settings on auto just in case the bow wave is too obvious...

Admiral346
15th Jun 2009, 21:48
Wing Root,

thank you very much for pointing me to that article. It makes for some very interesting reading, and gave me a lot to try out on my next flights.

If anybody finds that video, please post...

Nic

misd-agin
15th Jun 2009, 23:08
tubby linton -

MyFCOM VOL1 states that the gain adjusts receiver sensitivity to enhance ground mapping in MAP mode only.

In FCOM Vol 2 it states that gain should always be left in automatic,unless specific display enhancement is deemed necessary.

The majority of my colleagues use manual gain outside the terminal area as the radar appears to understate the weather.

*********************************************************

Friend checking out on my equipment. Met him on the ramp. He warned about moderate to severe turbulence near top of descent.

Me - "Yeah, that's stuff been there for several days."
Him - "Our radar didn't show a thing."
Me - "What radar settings were you using?"
Him - "I started using my old a/c radar settings(manual gain/tilt settings) but the CKA(TRE) said "we don't run the radar that way".
Me - "I use the same techniques you mentioned. Your instructor flies the line twice a year. Trust me, most guys don't use the 'book' settings out here."

Caveat emptor

Towhee
16th Jun 2009, 00:49
by Dr. Khatwa, from the 2007 Conference proceedings, is at this website:



http://www.atec.or.jp/FSF_2007_SEL.pdf

on p. 99/103


It's in Japanese; maybe someone has time to translate it.

Towhee
16th Jun 2009, 00:52
by Dr. Khatwa, presented at the 2007 conference, can be found at this
website:

wwwDOTatecDOTorDOTjpFORWARDSLASHfsfSPACE2007SPACEselDOTpdf


It's in Japanese, however; perhaps someone has time to translate it.

Graybeard
18th Jun 2009, 12:19
EGMA: "Re the comments on weather radar. It shouldn't be forgotten that radar cannot see through cells. It may be that AF avoided a cell only to find a massive cell hiding behind it."
-----
The above post at about 0119z remains, yet the following reply at 0240z was deleted: why? The mods are especially aggressive at deleting weather radar discussions, but seemingly not weather reports.
-------

That statement is true of the old X-band WXR designs prior to 1982. C-band radar does not have such a limitation. C-band will penetrate heavy precipitation better than X-band, but will not detect the lightest precip seen on X-band. (Airborne C-band wx radar is 5.4 GHz, and X-band is 9.3 GHz; your microwave oven is S-band, in the 2.2 GHz range.)

UAL had always chosen C-band radar up to that time, and continued with it into the Arinc 700 era, up until about year 2000. Air France was the only other major carrier to select C-band Arinc 700 WXR, which was discontinued about the time UAL abandoned it. Only Collins produced both C band and X band WXR in that era.

Collins pioneered PAC, Path Attenuation Compensation, in the 700 WXR, which would increase the receiver gain when it sensed reduced cell penetration. When it sensed it might not be able to detect the "cell behind the cell," it displayed PAC Alert, a yellow arc on the outer range ring behind the area of high attenuation.

RCA - (bought by Honeywell) Arinc 700 WXR had the same function they coined, REACT. I don't believe Bendix/Allied Signal/Honeywell RDR-4 series ever adopted that feature, but they may have.

In short, PAC compensated for the path attenuation of X-band weather radar, making C-band WXR almost redundant.

If the WXR is not pointing at the liquid part of the storm, path attenuation is not a factor, of course.

GB

john_tullamarine
18th Jun 2009, 12:39
The mods are especially aggressive at deleting weather radar discussions, but seemingly not weather reports.

On my watch, generally only pointlessly repetitive or unacceptably aggressive etc. posts are subject to edit or deletion.

It is not my role to dictate the direction of discussion, only to keep it reasonable and somewhat pertinent to aero tech matters. As regulars would appreciate, the great bulk of Tech Log posts are fine

I suspect that your comment probably is more relevant to R&N where there has been a need to keep some semblance of order.

Graybeard
18th Jun 2009, 13:05
You're right, Mr. Tullamarine, that comment was pointed at R&N mods, not Tech Log. It troubles me that a misinformed and speculative post remains, while a factual post is deleted.

GB

happybiker
18th Jun 2009, 19:14
Dr. Khatwa from Honeywell gave his presentation on the use and misuse of weather radar at the Flight Safety Foundation Conference in Seoul in 2007. I recall it was good presentation but I cannot find a link or any notes. If any member has a contact in Honeywell perhaps Dr Khatwa could be asked to provide a copy of his notes for this forum.

tubby linton
18th Jun 2009, 19:53
A summary of the presentation appeared in the UK Flight Safety Committee magazine for Winter 2008.If you cannot find a copy on the web email them and you will be sent a copy.

Towhee
18th Jun 2009, 22:30
The link to the 2007 conference is already posted above, in #23.

Can you not copy and paste it into google translator?

falconer1
21st Jun 2009, 11:50
hi folks,

do not know whether this is the right thread to post it, but coming back to square one would like to draw attention, like others have before me, to a very valuable web-site for pros and GA pilots alike..

Thunderstorms KILL!!! Get it ??!!

SmartCockpit - Airline training guides, Aviation, Operations, Safety (http://www.smartcockpit.com/pdf/flightops/meteorology/9)

falconer1
23rd Jun 2009, 19:36
it's CB season out there...

let's get into a heated discussion about WX radars here and its use..

let's post some provocative stuff here to lure the Einsteins of the engineering departments of the radar manufacturers into this thread..

AND the flight training managers, flight standards managers, and the good folks who change boxes ( sorry repair the radars) and stumble upon radomes that are our of spec at times..

any ideas???!!!

let's roll....

awblain
23rd Jun 2009, 20:15
This was posted to Qantas turbulence, but is more relevant here:

Do radar users have any views about how the weather radar interface and capabilities have changed over the last 40 years, compared with other aircraft systems? Could the desire for continuity in the way the data is presented
be preventing a more readily digested weather display from being introduced?

Back in the 1960s phosphor screens and 2kb memory reasonably demand manual adjustment of the scan direction; however, the availability of electronic scanning and beamforming and heaps of processing power should surely allow a more immersive product today.

falconer1
23rd Jun 2009, 20:27
and please I would like to be challenged on that..

the design inherent deficits of inflight wx radar cannot be and have not been adressed by the new technology we have nowadays, at least not to any measurable extent..

there have been good radars 30 years ago, I fondly remember a Primus 400 in a Falcon 20 in the early 80's..(high powered cloud slicer)

nowadays I look at an also very good modern Primus WX-880 in a Falcon 900EX..(again high powered cloud slicer)

magnetron based radars in short..

In between in the 90's I have seen some, at least in my humble opinion, horrible aberrations in WX radar design, from all manufacturers , in all kinds of different birds..(mostly "low-powered flash lights" whose limitations have been further emphasized by bad quality (read that as low transmissivity) radomes..

tubby linton
23rd Jun 2009, 21:08
Radar training is non existent and in my view is left up to the individual on the day to use whatever experience they may have using their own set.
I recently did a flight down the Eastern Adriatic in day time. The cells were well separated and with the radar in calibrated gain on range 120 miles it was showing only a very small green return on the route we were taking(probably only a couple of pixels).When I turned the gain to max it painted a large area of green and yellow.All I could see was high level stratus with no distinctive cummulus shape. We penetrated the area and it was a very smooth passage but at 31000ft and -43 sat we started picking up ice on the wipers for a few minutes.Before I penetrated the area I had swept the picture down to about -2 degrees to make sure there was nothing lurking in the cloud.
I was surprised at the difference between the two images that existed within one click of the gain from calibrated to max.If it had been night time and I had been in calibrated I wouldn't have seen the high level cloud and I probably wouldn't have seen the ice either until it may have had a detrimental effect on my flight.
Since the AF loss I have started to look much lower into a cloud to see what it contains and no longer use calibrated gain except at very short ranges.
Radar training has been very lapse across the industry and needs a serious reappraisal of training given to crews by the regulatory authorities.

PEI_3721
23rd Jun 2009, 21:11
falconer, I agree, and I’ll add to that – the low power digitally enhanced systems, with fancy displays and modes, do little more than the old systems did except they don’t do it as well.
The modern WXRs will detect the core of a Cb much the same as the old systems, but they do little if anything to provide information about the other hazards – ice, turbulence, and lightning. We have always avoided the core of Cbs; it’s the other hazards associated with Cbs which appear to be causing recent problems – together with modern ‘delicate’ systems.

New WXRs (and some teaching / sales literature) have given many of to-day’s crews a false sense of security such that they believe that they can ‘cut the corner’ - fly closer to the storm because it is more clearly defined. The problem is that the clearer definition is at the expense of deleting (suppressing) information, whereas with appropriate guidance from training and experience, the older systems provided much better information. My training on the older systems provided basic knowledge; in-service use with help from senior pilots provided knowhow.

Another aspect is the pressure of modern operation. Although few crews admit it, and many more fail to realise, current commercial pressures do filter through to operations – even subconsciously. Add to that, the ever increasing constraints in the airspace and operating rules, then most human willpower to fly safely can be pushed to the limit – it was OK last time so we can do it again.
Much of the above is reflected in conversations – the older style “should we be doing this”, whereas the modern digital enhanced approach is “how can we do this”.
Technology does not replace airmanship: - airmanship is the difference between ‘should’ and ‘how’, and some aspects of this can and should be taught

falconer1
24th Jun 2009, 22:14
could well be that the fact alone that the basics of inflight weather radar have not changed and will not change in the foreseeable future, simply because there's not much more to invent here, that all this sales marketing stuff, maybe the add some more colors with the next generation, and some more REACT and other features, obscures, for some, I may add, that nothing much has changed, except that I also find some new generation "low power" models pretty useless..

and the real reason for those radars may have been that some think that the solid state stuff is cheaper to operate and maintain compared to magnetron exchanges..

magnetrons on the other hand having some finite life and having to be replaced after a certain operating time..

and that naturally is not true either, as the low power stuff also breaks frequently, and it really does not make a diff whether you pay 10 grand for a new magnetron or the same 10 grand for some ICs..

PJ2
27th Jun 2009, 06:17
The pdf file at the following site is the best presentation on radar I have ever seen with possibly the exception of Dave Gwinn's:

Honeywell's Airborne-Weather-Radar Interpretation by Ian Gilbert
(http://www.gapan.org/ruth-documents/study-papers/Weather%20Radar.pdf)

Towhee
30th Jun 2009, 06:59
The Right Tilt

Honeywell's latest improvements to its current-generation weather radars include auto tilt to relieve pilots of having to make constant antenna adjustments to spot thunderstorms plus an upgrade to improve reliability for long-range flights.

As transport pilots know, the additional duty of constantly adjusting the radar antenna tilt is just another chore to manage. In addition, adjusting antenna tilt properly to spot storm cells and avoid frying into them requires some training and skill. The FAA has said training in the use of weather radar at airlines needs to be improved. Mistakes can and do lead to unpleasant encounters with turbulence. Avoiding such abrupt surprises will not only keep passengers and crews from injury in a high-G upset, it avoids a situation that could lead to an accident.

Some misidentified "clear air" turbulence encounters at cruise altitude actually involve thunderstorm cells bubbling up from below. Focusing the radar beam on what is happening at cruise level can totally miss these hazardous cells.

There may be very little in the way of rain to reflect the radar energy at cruise altitude, even though there could be plenty of turbulence and even hail. Hail, however, only returns 3% as much energy as raindrops. A thunderstorm below an aircraft's flight level and its true strength will be revealed best by directing the antenna beam to the freezing level where much of the rain is located, according to Stephen D. Hammack, manager of technical marketing for radar products at Honeywell Aerospace.

To make sure tilt is adjusted properly without any need for pilot involvement, Honeywell has created an auto tilt feature for its RDR-4B radar. Auto tilt can also be retrofitted onto the earlier RDR-4A model. Lance Okada, a Boeing 737-300 fleet standards captain for United Airlines, says auto tilt "reduces crew workload tremendously." The system is now certified for use on both Airbus and Boeing aircraft.

The manual technique used by most pilots is to set the radar antenna in "ground park" by lowering the beam until the display shows a little ground return at the outer edge. The radar is then set to detect thunderstorm cells. As the aircraft flies toward the cells out ahead, the thunderstorms "walk" into the beam and are picked up.

However, this technique does not work when a passenger jet is flying over water because there will be little ground return, even with high seas. "You almost have to memorize the correct tilt settings over water," Hammack says.

Tilt should also vary depending on the height of the terrain out in front of the aircraft so that ground return is minimized. For example, if an aircraft is flying into an area with flatlands off to the left of course, and mountains off to the right, the correct tilt for one would not work for the other. If the tilt is set correctly to minimize ground return over the flatlands, the antenna beam will be aimed too low for the mountains, and the display will be filled with ground clutter. And if the tilt is set to minimize ground return over the mountains, it will be too high to detect storms properly over the flatlands.

Honeywell has solved this with the auto tilt feature by dividing the 180-deg. area ahead of the aircraft into five sectors. The tilt can be varied five times during the 4-sec. sweep from left to right, for example. So each sector has the correct setting for the terrain involved based on elevations contained in the EGPWS database. The antenna sweeps at 45 deg./sec., and tilt adjustments from one sector to the next are just a few degrees at most.

Pilots typically fly at cruise with one radar set on long range (e.g., 150 naut. mi.) and the other set on short range (e.g., 30 naut. mi.). Several airlines teach pilots that once a storm is detected by auto tut, they should select manual and adjust the tilt to measure the top of the cell.
There are about 340 auto tilt systems in revenue service on Boeing 737s, 747s, 767s, 777s and the Ilyushin 11-96. This includes aircraft at United Airlines, Singapore Airlines, Japan Airlines, US Airways and Rossia, an airline in Russia. Supplemental type certificates (STCs) are also in process for the Boeing 757 and 767. Airlines pay about $6,000 per aircraft for auto tilt.

This Aviation Week & Space Technology pilot-editor saw the auto tilt function demonstrated on the Honeywell Convair 580, an aircraft that rolled off the production line right after World War II. The flight out of Boeing Field over Puget Sound was on a beautiful day, unfortunately, with nary a thunderstorm in the sky to demonstrate the auto tilt features. Seeing the Enhanced Ground Proximity Warning System (EGPWS) used in action for the first time proved quite interesting, however.

The system provides warnings well in advance of any terrain conflict by looking ahead and comparing the aircraft's flight path with a digital terrain database. The warning times are much improved over earlier generation GPWS systems. We flew to Port Angeles, Wash., and made an approach to William R. Fairchild International Airport there.

Then Honeywell test pilot Markus Johnson pointed the nose toward the high terrain of Olympic National Park where mountains rose to several thousand feet in front of us. The EGPWS map showed the elevations we had to be concerned about in red and yellow (at or above our altitude). EGPWS is designed to provide caution alerting up to a minute before a terrain conflict and to provide stronger warnings closer in.

This worked well on our approach to the high terrain with plenty of warning to pull up before closing in on the hazard. During a second pass on the same terrain, we employed the older GPWS in which there is no reference to a terrain database, just data from a radar altimeter looking straight down. When flying toward a precipice, as we were, the GPWS algorithms had little chance to spot rising terrain. The warning time was barely enough in this case, but we were VFR, and Johnson pulled up so we could head back to Boeing Field.

Another improvement that Honeywell has made to its RDR-4A and -4B weather radars is to make the antenna drive redundant. This project started out to meet the needs of Cathay Pacific Airways on its transpacific flights where radar outages have a greater chance of showing up on a long overwater leg. Previously weather radars have used a single azimuth and single elevation motor in the antenna drive, even though some aircraft such as the Airbus A340 are equipped with two receiver transmitter (R/T) units. As Honeywell notes, if either of the single antenna motors fails on the previous design, the radar is out of service.

Honeywell calculations show that if an aircraft makes 60,000 flights per year with an average duration of 5 hr. and with an azimuth motor providing 25,000 hr. mean-time-between-failure (MTBF), the airline will probably experience 19 cases of motor failure per year. These failures would cause an antenna outage and the loss of weather radar for the rest of the flight.

By installing the dual drive motors with the 25,000-hr. MTBF, Honeywell estimates there will be fewer than one antenna outage per year (0.03 per year). Since a single turnback due to loss of weather radar can be quite expensive, this $16,000 option (catalog price) can pay for itself quickly, Honeywell says.

About 200 of these dual drive upgrades have been installed on aircraft operated mostly by Cathay Pacific but also by Japan Airlines, Singapore Airlines, ANA and Rossia. While most of the supplemental type certificates so far have been for widebodies such as the Boeing 777 and 747 and the Airbus A340 and A330, an STC is in process for the narrow-body A320.

Honeywell's radar upgrade with dual antenna drive motors should cut out-ages to one per year on an aircraft
DIAGRAM: By providing two azimuth motors and two elevation motors on the antenna drive, Honeywell estimates antenna outages on an aircraft will drop to 0.03 per year.
~~~~~~~~
By David Hughes



from:
Aviation Week & Space Technology, 7/26/2004, Vol. 161 Issue 4, p47-50

Graybeard
2nd Jul 2009, 04:36
Motors aren't the only thing to fail on a WXR antenna drive. Scheduled overhaul of the whole enchilada at 10K hours is a good alternative, and means less weight and less complexity.

GB

tubby linton
2nd Jul 2009, 20:57
Does anybody have a copy of
"Airborne Weather Radar: A User's Guide by James C. Barr"?

PantLoad
3rd Jul 2009, 09:13
Gentlemen:


If your airline was worth a XXXX, it would provide proper RADAR training. Mine did. We spent two days with....not a training department pilot....but, an avionics eingineer. This was done on initial (when you're first hired with the airline as part of the basic indoc).

While it's true, using the RADAR is an art that is learned from experience, you have to be taught the basics...including basic SOPs regarding use, limitations, caveats, etc.

As stated many times previously, Airbus has great documentation to give some of the basics and overview. I don't know if Boeing has similar.

If your airline's SOP is inadequate, it's time to talk to your buddy in the training department to get the company up to speed.

Fly safe,


PantLoad

Graybeard
3rd Jul 2009, 13:06
Just found this white paper on the Collins Multi-Scan radar, which has been around since 2002: http://www.rockwellcollins.com/ecat/at/Whitepapers/WXR2100WP.pdf

It is instructive of the problem, and the solution.

GB

falconer1
4th Jul 2009, 08:06
Greybeard, sorry, am extremely skeptical about that..

maybe someone in this forum already has experience with that equipment..

but having been exposed to a wide variety of WX radars, installed in different airplanes, i.e. different antenna sizes, different radomes etc etc..I'm veeery skeptical..

I do not really buy it that automation in this regard, as well meant as it may be by the designers, and as logically as it may be explained, will solve the known issues..

my point is, that there are just way too many variables in the equation, and that is by the nature of WX radar technology and the elements involved..

or simply said, knowing all the limits of WX radar, I would not feel comfortable to rely on more automated circuits in a radar installation..

320 driver
4th Jul 2009, 11:21
Some of our airbuses have the autotilt function that adjust the tilt to get an optimum picture against clutter across the whole scan. I have to say, desite initial reservations, it does an impressive job and can provide a picture that I would struggle to achieve even with constant tilt adjustment.

Graybeard
4th Jul 2009, 12:26
All DC-9 and larger planes can house a 29" flat plate antenna with about a 3 degree beam width. Smaller planes require a smaller antenna, meaning wider beam width and reduced precision of the return.

GB

atrammell
15th Aug 2009, 20:21
The video by Archie Trammell you mentioned is now available on DVD or CD Rom. He publishes a monthly website also with training tips and techniques. Check it out: radar4pilots.com

Dream Land
20th Aug 2009, 02:52
Some of our airbuses have the autotilt function that adjust the tilt to get an optimum picture against clutter across the whole scan. I have to say, desite initial reservations, it does an impressive job and can provide a picture that I would struggle to achieve even with constant tilt adjustment. by 320 driverHave to agree, there was a bit of a learning curve involved, now when the other guy switches to manual and starts scanning around, I just give a sigh and ask that when he's done, please return to Auto, nuff said.

PantLoad
25th Aug 2009, 02:18
Actually, occasional change to manual mode is acceptable, but Airbus recommends exactly what Dream Land states.....returning to the auto mode afterward.

Personally, I use a combination of the two modes....I'm still not totally sold on the new dual-scan RADAR. But, please, don't throw rocks at me, I'm a slow learner.


Fly safe,


PantLoad

atrammell
4th Mar 2010, 15:25
Who wants to know about the study that cites the poor understanding of radar by professional pilots.

I have a copy,

Archie Trammell
www.radar4pilots.com (http://www.radar4pilots.com)

Checkboard
4th Mar 2010, 17:00
Hello Archie! I bought your full Radar course (Foolscap notes, "Severe Weather Flying book", Video & Jeppesen binder sized précis) in 1996. Best single piece of aviation info I have ever bought. Nice to see you're still about! :}

strmchs
24th Jan 2011, 20:30
It may also help if a crew understands the "stability of the atmosphere". The vast majority of red returns on a radar display are just large H20 drops, and may not be convective in nature. Weather attenuation is primarily a function of wavelength, not power. Knowing the stability of the atmosphere is crucial in correctly interpreting the radar display. Often it is the winds aloft that a crew may not pay enough attention to and that is one of the most important tools in analyzing how far and where to deviate. Non severe storms frequently have wind < 15 knots at altitude. A wx return that is severe will be there "because of the wind" and the stronger the wind the more dangerous the echo. This is especially true of targets in the mid latitudes of the U.S. I have found that understanding meteorology, especially in different parts of the world, the most beneficial tool in analyzing radar targets.

Sadly, the best teacher on radar and its limitations is now in Heaven. If you find any articles by Dave Gwinn, they will be worth reading.

STBYRUD
24th Jan 2011, 20:39
Our new ships have the new multi scan radar installed, and the auto mode is really quite something. Two sweeps (at least displayed sweeps, who knows what its actually doing in the background), one high, one low, and you got a picture, entirely free of ground clutter. All the way up to maximum range, the terrain database seems to be pretty accurate. Managed to show a fat downpour at just 2000ft agl from 40 miles away while we were still at 15000. Not too bad in my opinion. On other days though I could see what looked like a massive CB, but with no return on the calibrated auto view, turning up the gain showed something, but going to manual tilt at 0 / +1 showed it very clearly...

strmchs
9th Aug 2011, 22:55
Falcon,

THis new radar is very impressive. It can significantly reduce pilot workload. Collins did a tremendous amount of reserach with a BBJ and a research meteorologist that has done hundereds of penetrations in the Nasa DC-8. They used the results to program the algorithms into the database. I wish Id had the mutiscan in the 75/76 I flew. It has many other capabilities in addition to this. However, there is no radar today that can penetrate heavy weather and this is because of wavelength. X band radars can see tiny water droplets. S band Nexrad can penetrate much heavier wx because of its longer wavelength and thats why it was chosen by the NWS. Additionally the TDWR used by many airports now ( look on the back of the Jep 10-9 page) is C band radar and it also suffers from attenuation. Wet hail can cause significant areas of attenuation and some in the tower may not know this. The addition of Nexrad in the cockpit ( excluding of course operating over the tracks ) is an excellent tool to augment airborne radar. Often pilots write up a radar when its really a radome problem, i.e. water ingestion. This often occurs and is completely overlooked by maintenance. Note: I dont work for Collins.