Velocity Vector, a better way to fly IFR?

I want to start a discussion about how we fly IFR. This is not about anybody's brand of box, only about how we should present information.

I have flown a Tru Trak EFIS prototype and I've had several conversations with Jim Younkin about the human machine interface of how we fly IFR. I am pondering an article for IFR magazine so I would like to hear some opinions on the subject.

For those who may not be aware, The TT system Displays GPS ground track instead of heading, and gyrostabilized instantanous VSI instead of pitch. I am not positive what the roll display is, I am not sure if it is bank angle or turn rate.

I don't care whether or not people agree with way the TT EFIS derives the information, only the human machine interface HMI.

TT is chasing the LSA market with this unit, and some pilots have a problem with the unconventional HMI. Lets call it the velocity vector or VVHMI

If the LSA market is VFR only, then the reason for an EFIS in an LSA is to resolve an inadvertant IFR encounter. If that is the reason then the logical question is, which HMI would most likely result in a successful outcome.

I mentioned that I have flown the unit, and I can say without any doubt that a VFR only pilot could more easily fly IMC with VVHMI.

Some units no display both VV and traditional information. The military jets use VV information. ATC could start the trend by doing something as simple as adding a new word to their glossary, TRACK. Instead of "Fly Heading XXX" the could tell /G airplanes to "Track XXX" That would be a great first step.

Anyone with an EFIS hand flying the approach puts the track carrot in the course notch and the needle stays in the middle. Why not have the Track as the primary display with the mag heading as a carrot?

Same with pitch, AOA or a secondary indicator for actual pitch with IVSI as the primary indication. Isn't that what we really care about?

With that background, the question is this, If the VVHMI is easier to fly for a VFR pilot, why don't we abandon the traditional heading, and Pitch HMI and begin a transition to a VVHMI on all makes of EFISes?

For the record, I can argue both sides of some aspects of this argument, but with the proliferation of GPS and EFIS, flying the the old HMI just because we always have, is not a good enough answer.

Tailwinds,
Doug Rozendaal
F-1 EVO with traditional HMI

I would want both.

Doug,
I do not have any experience with the new VV EFIS systems but I do fly with a HUD velocity vector in the Air Force and I wouldn't want to give it up. In my opinion, it rapidly speeds up your instrument crosscheck. Set the VV level and cross check the VVI and Altimeter - done. Want to set 3 degrees on an ILS...set three degrees on the VV and cross check - you are now descending on a 3 degree glidepath and 300ft per mile. I agree that a VV would benefit a VFR pilot who encounters IFR.

Two caveats:
1) I do not rely exclusively on the VV...I also cross-check a standard attitude indicator in the process. I would consider it very poor form to only have a VV type instrument with no backup. I'm not sure about FAR requirements here...maybe others can address this? In your scenario, what happens if the required GPS goes TU?
2) Its easy to become reliant on the technology and lose basic skills. Similar to turning off a GPS and trying to read a map, turning off your VV and forcing yourself to fly standard instruments (or just maneuver VFR) can be a humbling experience for someone "addicted" to a VV - ask me how I know

I'm tossing around the idea of having a Dynon EFIS and a Tru-trak in my RV8...so thanks for the thread and I look forward to your article.

Doug,

About the same time I was going through my basic instrument training during my private I also got to fly a military avionics development simulator regularly at work. I found the VV presentation completely intuitive to fly with very little training (put the VV where you want to go ...). I think Garmin et al have significantly missed a trick by simply replicating steam gauges on glass. Chelton and GRT, as well as Trutrak, seem to have thought about how to get the most out of the new technology. So I am a huge fan of the VV type presentation. As very few GA pilots have flown with a VV most are unlikely to realize what they are missing! Once the enlightened start to make VV based systems more prevalent their popularity will increase as more people understand the benefits its brings.

I have recently finished my IR (after many years of VFR only flying), the airplane I did most of my training in did not have a GPS. Transitioning into an IFR GPS equipped airplane made tracking localizers (and VOR radials) so much easier - intercept and get the needle centered, then make the track number the same as the inbound course - easy (right!), but certainly better than trying to guess the wind. As for glide slope, I had never thought how a VV could be of benefit until John pointed it out above.

IMHO a VV equipped system is the way ahead, once pilots brought up on steam gauges realize what they are missing everyone will want one.

Pete

Great topic Doug!

I have been flying with VV guidance for many years in a certain "Heavy Glider", and use it almost exclusively (with pitch/roll cross-check for situational awareness). In my RV, I have it on the GRT, and use it for approach guidance all the time, as well as for quickly nailing a level-off. I've flown experimental VV guidance systems in many different simulations, and they are all easier to fly than raw data.

I have flown the TT ADI quite a bit in Louise's -6, and find it equally as easy for nailing altitude. I'm not sure I'd want to be without a true attitude reference as a backup, but yup - VV is a far easier way to fly IFR, based on my experience.

Paul

I want them both

I agree with Paul and the others that the indicator that shows what the aircraft is doing in three dimensional space without lag and without requiring the mental integration of a VSI to an AI is a big plus. That said, I still want to know the airplanes attitude. GRT has both at once if you turn on the appropriate indicators.

Both in reaching/holding altitude and in the synthetic approach (HITS), the path indicator is a wonderful thing. In the GRT it also shows where you are going while crabbed, with the airport drawn on the brown/lower side of the screen right where it is if you look out the window and can see it. I'm sure others have this, too, but I'm only familiar with the GRT.

I know I don't have to explain it to this crowd, but it does matter what the aircraft's attitude is especially when it does not agree with the path!

BTW - these features are very helpful in poor VMC, too.

TT Functionality

At its little functional heart, the TT is a Turn Coordinator with a VSI in the middle. It is a stretch to use the term Velocity Vector (or Flight Path Marker) when describing the VSI function, and indeed, even the term CDA (Climb-Dive Angle) is not appropriate since no angular information is available without integrating an airspeed term.

The TT roll display likewise does not yield angular information. A steady-heading sideslip with a wing down 20 degrees will result in a wings-level TT display.

This is not to say that the instrument is not useful. It is a better global information-processing display than a separate iVSI and Turn Needle or Coordinator, but the control capabilities are basically the same.

Doug raises some interesting points in terms of future training. As more and more people are exposed to VV systems, I would hope that training will emphasize the obvious benefits. One of the interesting results to come out of the polling of several groups of HUD-experienced Carrier pilots at PAX River concerned the utility and necessity of displaying raw pitch-angle data as a Waterline symbol in the HUD. Other than the obvious role in providing attitude information when the VV system failed, the only time when pilots envisioned a clear need for a raw pitch-angle reference was to initially set and hold the nose attitude at liftoff when carrying heavy high drag stores (like mines) on cat shots or land takeoffs until the VV and AOA settled down.

First of all, I would like to say again, I am not interested in a discussion about TT ADI or EFIS. It is a discussion about choosing a different paradigm in instrument flying.

Experimental aircraft have been leading the charge in many areas, and I think the industry needs to have a discussion about what the HMI looks like in the future.

Jimmy Doolittle and Sperry developed a great system with the available technology, but I think we can, and it is time to do better...... What better place than all the new EFIS technology that is arriving in the EXP market.

I don't know what "better" means, it maybe synthetic vision coupled with Velocity vector, but again based on the synthetic vision systems I have seen, the pitch gets lost in teh pretty picture, the horizon is far below the center of the instrument and the perspective of pitch gets lost in the perception of altitude.

Tailwinds,
Doug

Yes, your comments are on the money !
With our synthetic vision you "see" where you are going - but you are right, the vertical is difficult to do this way with any sort of meaning. I am very open to ideas and will be keenly watching this thread...

Of course I've been looking at how other systems try to do it - but to be honest, I don't really like any of them - there has to be a better way. Little abstract pointers and things don't do it for me. I'm stupid - I need the EFIS to be "loud and clear".

Rainier
CEO MGL Avionics

B25Flyer said:

First of all, I would like to say again, I am not interested in a discussion about TT ADI or EFIS. It is a discussion about choosing a different paradigm in instrument flying.

Experimental aircraft have been leading the charge in many areas, and I think the industry needs to have a discussion about what the HMI looks like in the future.

Jimmy Doolittle and Sperry developed a great system with the available technology, but I think we can, and it is time to do better...... What better place than all the new EFIS technology that is arriving in the EXP market.

I don't know what "better" means, it maybe synthetic vision coupled with Velocity vector, but again based on the synthetic vision systems I have seen, the pitch gets lost in teh pretty picture, the horizon is far below the center of the instrument and the perspective of pitch gets lost in the perception of altitude.

Tailwinds,
Doug

Click to expand...

Track better than heading

I have found flying the ground track based HSI on my GPS496 is much more intuitive and precise than flying a magnetic heading on a standard HSI.

Approaches & airways all want a ground track. ATC also wants a ground track, which is why they sometimes hunt for the right heading in strong winds.

Bottom line is than it is always better to know what direction you are going than what direction you wish you were going.

What I would like is GPS track merged with magnetic heading, such that below the velocity suitable for GPS track, magnetic heading took over (ground ops). That could be done in a relatively seamless way via software. Also, magnetic heading should seamlessly back up the GPS in case of failure.

As far as pitch I don't have a strong opinion yet. I have and ADI pilot I use for AP functions and I guess it provides a backup AI function. I'm going to try flying it a bit and see how it works.

I think some people get nervous betting their lives on GPS. Its important to remember the number of people who have bought the farm because of vacuum system failure in IFR. All systems can fail. The key to long life (IMO) as an IFR pilot is heterogeneous backup systems.

I have 2x Dynon D10s, both with backup batteries. One I use for everything but heading. The other configured as an HSI, one button away from being a backup AI.

The problem is that both units rely on the pitot system to make the AI work properly. I would strongly prefer that one or the other unit be configured to use GPS ground speed for AI solution rather than air speed.

If I have a pitot failure IMC, I'm going to have a very bad day. I don't know if the ADI pilot needs airspeed or directly reads rate of turn (If you know, let me know)

Sorry for being so dumb, but can someone describe how the VV is depicted on one or more of the systems? I've studied the displays shown on various manufacturers' websites, for example, but it doesn't jump out or maybe it isn't displayed.

I am very interested in the human/machine interface, and appreciate Doug's starting this thread.

I've been flying velocity vector's around for about 10 years & absolutely love them. They are great for many things other than IFR flying. However, a velocity vector alone is not enough, IMHO, for IFR flying. For IFR work, I still want a bank angle displayed along with pitch attitude of the plane & mag heading. If everything is displayed correctly, you can get ground track easily by comparing the VV to the heading. Is the current standard of displaying attitude & VV the best? Maybe, maybe not. I like it, but I could be swayed if someone can make something better.

Alex, great question - many people haven't flown with a velocity vector, so this is worth talking about. To describe what a velocity vector (sometimes also called a flight path marker) does, I'll use this generic EFIS screen (that I happened to program up for my homebrew EFIS...it does look somewhat similar to a "Brand B" EFIS ).



In that picture, the heading tape is shown across the bottom. Airspeed is on the left & altitude is on the right. Vertical speed is shown as a while bar with text just to the left of the altitude. The black "W" represents the waterline (aka Whisky line) of the airplane (i.e. where the nose is pointed) and is fixed on the screen. The velocity vector is the green circle with little wings & tail. Things can be moved around, but the generally accepted EFIS/HUD layout is airspeed on the left, altitude on the right & heading either at the top or bottom. Heading can also be displayed along the horizon line - that works fine too.

The "W" shows where the nose of the airplane is pointed. That works just like the aircraft reference on an old-school attitude indicator. The shape of the "W" symbol is not critical & can, in fact, be changed to include flight director type information & more. Aircraft heading and pitch attitude are shown relative to this symbol.

The velocity vector moves around the screen relative to the W and horizon to show where the airplane is actually going. In the above picture, the aircraft's pitch attitude is about 5 degrees up (see where the "W" is on the pitch ladder). The velocity vector shows that the airplane is actually descending at about -5 degrees (center of the velocity vector circle). The vertical (i.e. pitch) difference between the "W" and the velocity vector conveniently works out to be the airplane's angle of attack (if you define zero AOA as aligned with the "W"). So, the above picture shows the airplane at about 10 degrees AOA. If the airplane is moving level, the velocity vector is drawn on the horizon. If the airplane is descending at 3 degrees, the velocity vector is drawn 3 degrees below the horizon (ILS anyone?). If the airplane is moving straight down, the velocity vector is drawn at 90deg down.

That's pitch...half of the velocity vector. Yaw (sideslip, beta, track - whatever you want to call it) is the other half of its job. The above picture doesn't really show this well, so here's one that should help.



The display here is roughly the same except that the velocity vector is yellow. Here my airplane is flying level, but with a significant crosswind from the left. Since the airplane is flying level, the velocity vector is drawn on the horizon (that's the pitch part). Since there is a crosswind from the left, the airplane is actually moving (drifting) to the right of its nose. So, the velocity vector is drawn to the right of the "W." The difference between your "W" and velocity vector here is your drift (the difference between your heading & ground track).

Displays should be programmed so that a degree up or down is equal to a degree left or right on your EFIS. So, this shows that I have about a 20 degree difference between my heading and ground track (it was freakin' windy). If the EFIS has a heading tape instead of just a digital readout, the ground track can be read by drawing a line from the velocity vector down to the heading tape (when your wings are level).

For day VFR-only flying, I still like having an attitude reference, but you certainly don't need one. For night VFR flying, I REALLY like having an attitude reference. I flew a VariEze around for about 5 years without any attitude reference (except the huge attitude indicator out the front window). (note: I don't count that 2" turn & bank as an attitude reference...paperweight) Love it:



(on soap box.) Without getting too caught up in the source of the info, I think it's important to think about what the pilot is actually being shown. Pitch based on vertical speed & bank based on turn rate are not actual "control parameters." While you can fly around & maintain level with a VSI & turn & bank, they can't be relied on in all situations - especially dynamic situations. I still feel that attitude derived from a gyro source is a safety critical item for IFR flight (gyro source: EGI, INS, AHRS, MEMS, mechanical gyro, etc). A non-gyro device might save your life if you get in a bind, but complacency around using it might kill you. (off soap box.)

I'm very much for us pushing the human-machine interface (aka pilot-vehicle interface (PVI)). There are several EFIS manufacturers that read these boards, so your great ideas just might make the next round of software (get your patents filed quickly ).

Hope this helps!

Groucho, excellent explanation. One curiosity though - the Blue Mtn. picture shows constant altitude flight (vertical velocity vector level), but nose down (W below the white horizon line). ??

Classification of Velocity Vectors

The terms Velocity Vector and Flight Path Marker are often loosely applied to three distinct implementation schemes that behave very differently:

1. The symbol is caged to the fuselage boresight laterally and only moves vertically (in the same plane as the fixed Waterline.)

2. The symbol is air mass-referenced and shows actual projected path (including Beta sideslip angle) through the air mass. This is the implementation of choice for Air-to-Air weapon systems, and is most convenient for any maneuvering flight reference.

3. The symbol is ground-referenced, including drift over the ground as well as Beta, and thus shows the true flight path projection in reference to objects on the ground. This is the implementation of choice for Instrument Approaches and Air-to-Ground weapon delivery.

The most effective HUD presentation that I was able to evaluate in a sim was a "Best Of Both Word's" approach from the British for their last group of Sea Harriers. The standard 'circle with wings and a fin' symbol was displayed as an air mass reference (they called it the CDA, or Climb-Dive Angle indicator) and another small diamond symbol was shown full time as a ground-referenced Velocity Vector. The diamond was carefully mechanized to avoid clashing with the CDA when there was minimal drift over the ground.

Alex,

Let me put it in warbird pilot speak, Our traditional HMI, or PVI, shows us where the airplane is pointed. VV shows where the airplane is going.

Most systems that incorporate VV info today provide it as secondary information, with pitch roll and heading primary.

Displaying VV as primary with pitch roll and heading as secondary information should result in an interface that is much easier to fly. As has been said here many times, most of us with EFIS are now the flying track carrot instead of the heading on approaches now.

I was absolutely opposed to it and I told Younkin he was on the wrong track with his EFIS interface until I figured out that only reason for an EFIS in a light sport is inadvertant IFR. (I realize I am repeating this) When I realized that a Sport pilot would have a much greater chance of survival with VV instead of tradtional pitch & roll info, then I asked myself, if it is easier for them, why isn't the industry having this discussion instead of just Jim Younkin, who by the way, has probably pioneered more flight control and insturment technology than anyone.

Repeating again, I am not interested in discussing how we derive that info and GPS failure etc. Once the industry decides what the correct interface is, then we can discuss how to get the info. There are plenty of failure modes in what we are doing right now.

Tailwinds,
Doug Rozendaal

AlexPeterson said:

Groucho, excellent explanation. One curiosity though - the Blue Mtn. picture shows constant altitude flight (vertical velocity vector level), but nose down (W below the white horizon line). ??

Click to expand...

Excellent catch...I'm pretty sure that was in an updraft, so it took some nose down to maintain level.

I set my "level" in my EFIS to correspond to cruise speed at about 8000' MSL, so it shows 0 AOA at cruise speed. Anything slower than cruise, it shows positive AOA & anything greater than cruise speed it shows negative AOA. A negative AOA at 14,500' means I was pushing forward for something (updraft!).

Here's another possibility (not real, but to use as an example)...Suppose I just pushed forward on the stick to get that nose low attitude. Since the gyro in the EFIS outputs measured angles, the attitude of the plane is shown immediately. The vertical speed takes a few seconds to "catch up." Because of that, if a pilot is using a pitch attitude display based on vertical speed, that pilot has to give a control input & wait to see if it was right. A pilot using a "real" gyro can change his pitch attitude a degree (or whatever's required) and get instant feedback. Both can be done, but a vertical speed based system requires the pilot to fly more "open loop" (less frequent control inputs).

For inadvertent IMC, a pilot might be able to survive using either system. Whatever the sensor input to the display, (historically speaking) an non-IFR trained pilot typically doesn't stand that good of a chance. Like others in the thread say, pushing the PVI/HMI technology forward is one great way that we can increase the chances of survival for VFR pilots in inadvertent IMC.

Thrust + Attitude = Performance

The correct technique for instrument flying is to set an attitude and a power and monitor the performance instruments (airspeed, altitude, heading, v/s) to assess. Any errors should be corrected on the attitude and/or thrust. It is extremely poor technique to attempt to fly the performance instruments which results in "chasing" parameters. Having said that, I have seen an awful lot of pilots who get away with it on a regular basis!

The VV or FPV (whatever you want to call it) is essentially a performance instrument. Whilst it is a fantastic tool it should not be used as the primary means of controlling the attitude of the aircraft.

paul330 said:

The VV or FPV (whatever you want to call it) is essentially a performance instrument. Whilst it is a fantastic tool it should not be used as the primary means of controlling the attitude of the aircraft.

Click to expand...

Paul, That's a great quote from the text book, and I guess from a few hours of practical experience flying "conventional" glass. The suggestion here is that a VV, properly implemented, will provide better information for the pilot to control the aircraft. It may require some tweaking of what are thought of as instrument flying basics (I'm not sufficiently knowledgeable or experienced to say). But I would suggest one of the reasons for the current teaching is that, generally, there is no indication to the pilot where the aircraft is actually going. Once you have that, the basics of set the attitude and see what you have may be less relevant. Good technique will still play a part - and chasing anything is often a bad idea - but focusing on where you're going, while keeping the other parameters in bounds, has got to be a good thing?

REHughes said:

The most effective HUD presentation that I was able to evaluate in a sim was a "Best Of Both Word's" approach from the British for their last group of Sea Harriers.

Click to expand...

Thanks for that, I had a small part to play in the design of that system. One other way to differentiate between a ground referenced and an air mass referenced system is to have 2 modes (perhaps called air-to-air mode and air-to-ground mode), but in reality won't we be interested in the ground referenced symbol most of the time?
Pete

penguin said:

Paul, That's a great quote from the text book, and I guess from a few hours of practical experience flying "conventional" glass.

Click to expand...

Er, actually 13000+ hrs including a RAF Flying Instructor on basic and F4 and currently a IRE/TRE on Airbus 330/340...........

You don't need the FPV to tell you where the aircraft is going. Basic technique is to know the appropriate attitude and thrust setting for the phase of flight. It's as relevant on what I fly today as it always has been. I teach to set the parameters and THEN see what the FPV is giving you. It's a great tool and source of additional information but no substitute for basic IF technique. Trust me on this from one who, when young and foolish, used to fly around over the UK North Sea, low level at night at 450kts doing 4g turns on instruments!!

not to hijack the thread, but what current systems on the market offer a flight path marker (velocity vector)?

Jeff

My head hurts!

The only thing I understood so far is that mechanical turn coordintaors are indeed paperweights....

Frank

frankh said:

The only thing I understood so far is that mechanical turn coordintaors are indeed paperweights....

Click to expand...

Same here, regarding the "head hurting" title. I've read all this several times and keep thinking of other notions I've heard over the past few years, such as.......

"Don't use the GPS as the primary navigation instrument. Only as backup."

Does that make sense in this day and age? Of course not! Even some, "by the old methods" flight instructors attempt to keep GPS's out of students hands, while some advanced schools start with " GPS glass" on day one!

I'm a guy that's tracked probably all flight into terrain accidents for several decades, and am familiar with a bunch in the 50's too. I'm extremely open to new technology, and don't feel that the way "it's always been done", is always the right way now.

L.Adamson

Great discussion. Keep the info coming I am learning a lot from this thread and appreciate the time people are taking to share their knowledge.

As I approach needing to make decisions on instrumentation everything I can learn is helpful. I make my living working with technology and learned years ago that technology for technology sake is a bad choice. Use it if it improves the process, increases efficiency, adds a safety factor, or a combination of the above. Otherwise it is a waste of time and can be dangerous.

GOOD QUESTION............

jeff122670 said:

not to hijack the thread, but what current systems on the market offer a flight path marker (velocity vector)?

Jeff

Click to expand...

Who has this now in their systems?..........................

jeff122670 said:

not to hijack the thread, but what current systems on the market offer a flight path marker (velocity vector)?

Jeff

Click to expand...

Our Enigma and Odyssey do horizontal velocity but not as a seperate indictation - rather by means of the synthetic terrain being based on ground track. In other words, if you are approaching an object, such as a runway, you keep it in the middle of the screen and you get there...

Based on this thread - I started thinking a little, and then I started hacking a little.

So, as of the next update for both Enigma and Odyssey - I have added a few things. You now get a vertical marker that moves up and down and is related to the synthetic view on the screen. I.e. - if you approach a runway you keep the runway in the middle and the vertical marker on the threshold of the approaching runway on the screen - and that is exactly where you will end up. The marker banks with the image so it it not dependent on attitude - just true flight path.

For those that would prefer to use the synthetic vision based on heading rather than ground track, I've added this as an option. In this case the velocity marker will of course move left and right as well as, in effect, it is ground track. Personally, I prefer the synthetic vision based on ground track - it seems more natural when flying the EFIS.

Thanks for the thread - it's been interesting and valuable...

Rainier
CEO MGL Avionics

Gimme needle, ball and airspeed...

REHughes said:

This is not to say that the instrument is not useful. It is a better global information-processing display than a separate iVSI and Turn Needle or Coordinator, but the control capabilities are basically the same.

Click to expand...

It's interesting you say this... When flying IFR in my spam can Grumman Traveler with pure steam gages I always look primarily at the Turn Coordinator for lateral guidance.

Initially, my reasoning was if my attitude indicator failed I would have an easier time transitioning to partial-panel, turn coordinator-only instrument flight. Now, years later, I've decided it's easier to fly PERIOD using the turn coordinator for primary lateral guidance.

Of course, I take the occaisional glance at the attitude indicator (and other gages) to verify what the TC is telling me, but I find the very slight lag (compared to the attitude indicator) in response of the TC doesn't have me "chasing" an attitude like the attitude indicator.

Even should I become disoriented I believe the TC is more valuable:

-- Throttle idle
-- Trim for best glide
-- Release yoke
-- Center needle (and keep centered) with rudder
-- Wait until vertigo subsides, or you drop out the bottom of the cloud (hopefully before you hit the ground ;-))

This discussion reminds me of my experience in choosing cockpit instrumentation when outfitting the Grumman. I decided early I needed a situational awareness aid. I narrowed my choices to either an HSI or a moving map display. Since I coudn't afford an HSI I wound up with a MM GPS/Comm.

I'm glad I did, because since then I've decided a MM is LIGHTYEARS ahead of an HSI for improving SA. I know there are a few HSI hardcores out there who swear by the things, but a MM requires NO mental gymnastics to nail your position in relation to anything displayed on the map -- remember all those silly questions on the FAA IFR test?

Likewise, determining a heading for a new clearance is a snap -- just look at the map, turn generally in the direction you need to go and "fine tune" yourself after setting the freqs in the nav radios.

Much like this, I believe the new crop of VV instrumentation will prove out in the end because it eliminates the "intrepretation" step in instrument flight. I can simply look at the gage and "see" what the plane is doing and where I'm going. With conventional instrumentation I must look, then interpret (hopefully correctly) what the gages are telling me before I know.

I think the less experience one has with the "old" stuff the more useful he/she will find the "new" stuff.

Regards,
Mark Sletten

Control -vs- performance instruments

The correct technique for instrument flying is to set an attitude and a power and monitor the performance instruments (airspeed, altitude, heading, v/s) to assess.

Click to expand...

Exactly spot-on correct statement. I taught basic control-performance flying from 1987-1991 in the T-37. We hammered on students all day to get this right.

The only thing you have direct, immediate control over is what you hold in your hands: stick and throttle. Or said another way, attitude and thrust. These things are called "control" parameters, and so the attitude indicator and what ever you use to indicate thrust are called "control instruments".

Everything else the airplane does is a reaction to whats done with the control parameters. Those things are called "performance" parameters, or instruments. Examples of performance parameters are airspeed, vertical speed, altitude, heading, etc. And yes the VV is also a performance parameter. Its closely tied to the attitude of the aircraft, but in the end its just another thing to chase. We don't have immediate direct control over this.

Control/Performance trained students are taught to set the controls first, and then assess the performance. Control is managed; performance follows. If performance isn't where you want it, you make a change to the controls and re-asses your performance. Its a loop.

I use VV as a matter of routine in my current line of work, but find it really only marginally useful on approaches to set descent angle. To date, with 12000+ hours, I cannot use VV to hold altitude. Its not sensitive enough.

John Collier said:

2) Its easy to become reliant on the technology and lose basic skills. Similar to turning off a GPS and trying to read a map, turning off your VV and forcing yourself to fly standard instruments (or just maneuver VFR) can be a humbling experience for someone "addicted" to a VV - ask me how I know

Click to expand...

Hehe - we used to say the same thing about the F-15 pilots relying on all their newfangled technologies (I was a Phantom jock). I think it is always a good argument to have the uncorrected raw data available as an option, and to spend time training using only the raw data. "If you don't know what the interpreted data means, you can't know if it is lying to you."

I'm tossing around the idea of having a Dynon EFIS and a Tru-trak in my RV8...so thanks for the thread and I look forward to your article.

Click to expand...

That's what I'm installing, along with a GNS-480 which should drive the TruTrak through any approach without possibility of pilot error - err, for the convenience of the pilot. But I still plan on flying most of my approaches referring only to the needles, attitude, airspeed, and VV etc. The other stuff is there to measure how WELL I fly the basics...

Cheers,

Bill

VVI way to go for F-15 Bravo

In the back seat of an F-15 I couldn't fly without the VVI, In a pitch sensative aircraft VVI really helps you stay ahead (sts) of the aircraft. VVI is constantly in my crosscheck. Boys up front get the HUD with flight path marker that much like the VVI gives you instant trend forcast. F-16 doesnt seem to have that same pitch sensativity, of course I get a HUD repeater when flying Viper bravo, so I use flight path marker instead of VVI.

Seriously, from a human factors prospective, in a pitch sensative airframe you need something to provide instantaneous trend or you'll be chasing the needles. I wont be adding a VVI to my panel but will rely on trending from EFIS much like you describe.

Bill Wightman said:

The only thing you have direct, immediate control over is what you hold in your hands: stick and throttle. Or said another way, attitude and thrust. These things are called "control" parameters, and so the attitude indicator and what ever you use to indicate thrust are called "control instruments".

Everything else the airplane does is a reaction to whats done with the control parameters. Those things are called "performance" parameters, or instruments. Examples of performance parameters are airspeed, vertical speed, altitude, heading, etc. And yes the VV is also a performance parameter. Its closely tied to the attitude of the aircraft, but in the end its just another thing to chase. We don't have immediate direct control over this.

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In all the Tactical Aircraft Head-Up Displays that I am aware of, the Velocity Vector (or Flight Path Marker) is THE control parameter used to set attitude. The Angle Of Attack symbology, Approach guidance cues, and Potential Energy indicators are all referenced directly to the VV/FPM symbol. Fuselage Pitch Angle, if displayed at all, is generally not used for anything as long as the Flight Path system is working.

A Level Speed Change maneuver can demonstrate how the two different control parameter systems function:

With an Attitude Indicator, you start out with, say, 10 degrees nose up at 100 KTS, and as you add power and accelerate, you roughly adjust a constantly-changing AI to maintain a constant Altitude value (using the VSI as a leading-indicator) and you eventually wind up at 3 degrees nose down when you have accelerated to 180 KTS.

With a Velocity Vector system, it is a whole lot easier. Keep the VV on the Horizon Line as you accelerate, making tiny changes up or down as you reference the performance parameters, the Altitude and VSI.

I am assuming that your Flight Guidance commands in the Boeing are referenced to the Waterline Pitch Symbol, making it the control parameter, and relegating the VV to an accessory Descent Path type indication. It might be the result of my background, but I much prefer the Velocity Vector referenced systems, even in Head-Down displays.

Flight Path Marker or VVI

gasman said:

Who has this now in their systems?..........................

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GRT has it.

At first you may ask what it (VVI) is doing especially in strong manuvers. Once you know what it is telling you it makes flying easier.

A couple of examples, on final in a strong crosswind you put the VVI on the runway on the PFD and that is where the airplane will go. The nose of the airplane will be pointed away from the runway (depending on the strength of the crosswind) but the track will be to the runway. The GRT shows both lateral and vertical vector in one indicator. Put the VVI where you want to go, it's that easy.

Another example is leveling off after a climb or descent. Simply put the VVI on the artificial horizon at your target altitude. Once the VVI is on the artificial horizon theres no climbing or descending, you are level at the altitude you want, no guessing. If you want a 3 degree descent, put the VVI on the 3 degree pitch line.

It makes steeps turns under the hood a none-event.


Regards,

Carlos Fernandez
GRT Avionics

VV for instruments -vs- tactical

Robert, interesting reading your post. I have no experience in tactical type aircraft, but there's obviously a whole raft of things y'all use VV for in the tactical world.

I've flown many of the heavy aircraft, Boeing and Airbus both. They use what's called "split cue" flight directors. This type of flight guidance simply shows the pilot where to put the airplane in pitch and roll. The other common type of FD display is the "v-bar" type.

But, in all the ba-gillion of instrument hours flown in the commercial arena, the VV is vestibular in existence. Its not been found to be helpful in the instrument flying world, at least not in this industry.

And so for sport airplanes, maybe there's a middle ground for VV usefulness (?) Looks to me like the current crop of AHRS driven PFD's now in place have taken much of their design cues from the commercial glass displays. Maybe that explains the relative lack of VV driven data in these displays.

Bill Wightman said:

Robert,
And so for sport airplanes, maybe there's a middle ground for VV usefulness (?) Looks to me like the current crop of AHRS driven PFD's now in place have taken much of their design cues from the commercial glass displays. Maybe that explains the relative lack of VV driven data in these displays.

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Perhaps, yes.
As mentioned in my previous post I've added this to our EFIS systems now - and will be giving it a spin in our test aircraft in the next days (I've been a little reluctant in the past - but this thread actualy pushed me).
Granted - you can fly IFR perfectly without it.
What is the real value ?
The only one I can really come up with so far - could be useful.
If I have an engine out on finals I would see on my EFIS screen exactly whether or not I will be able to glide to the runway - considering I've got stacks of wine estates and fields on finals - that could be a good thing.
With the synthetic vision, it gives me a good idea just about anywhere where I would end up in a glide - so perhaps that is not bad.
Apart from that - hmmm, not too convinced yet...
That is why I also added a little menu setting to switch it off...

Rainier
CEO MGL Avionics.

Rainier,

Excellent. No telling what this group of sport flyers will come up with. This group of pilot/builders represents an incredible cross-section of talent, experience, inexperience, imagination and determination.

One thought: could / would it be possible to add a simple flight director to these PFD's? That would be a NICE addition for IFR flying.

Bill Wightman said:

Rainier,

Excellent. No telling what this group of sport flyers will come up with. This group of pilot/builders represents an incredible cross-section of talent, experience, inexperience, imagination and determination.

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Yes, you hit the nail on the head. The wealth of opinion on just about anything available on Vans and similar lists is an excellent source for any EFIS builder and since we do experimental, uncertified EFIS's it can take as little as a few hours to add a new feauture or modify one (or get rid of something).
As there is no such thing as a stupid idea - I certainly listen to anything. Yes, we fly ourselves and this gives us a good idea what a pilot wants or needs - but we certainly don't know everything. I'd reckon a good 50% of functions and features available on our units are as a direct result of input from others. It works.

One thought: could / would it be possible to add a simple flight director to these PFD's? That would be a NICE addition for IFR flying.

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Most of that is in. Integration with SIDS and STARS is about the only thing we still need to do. That is likely to come when we start with Jeppesen. Now that PocketFMS navigation data is up and running in addition to our own - Jeppesen is next.

Rainier