View Full Version : Are Needle and Ball Obsolete?

05-10-2008, 05:11 PM
(The excellent thread on IFR philosophy raised a question that I thought deserved it’s own discussion, so rather than lead that one astray, I thought I’d start another…)

OK, here is a question that my raise the ire of the more experienced pilots in the room - is flying by needle, ball, and airspeed obsolete? Now before you get out the pitchforks, torches, and AN Low Frequency Range receivers, let me elaborate…..

There is no doubt whatsoever that no matter what airplane you are flying under IFR, you need to have backups in case of failures. In the old days, we all learned that if you lost your vacuum pump, you were going to lose the Attitude Indicator and DG, so you were left with the Turn and Bank, Airspeed, and Altimeter - a daunting and difficult prospect under the best conditions and level proficiency, and seat-clenchingingly difficult in the bumps. We’ve all been there….but will current and future students of instrument flying need to be?

I believe that we need to adjust the way we think as technology changes. In fact, this isn’t really a different way of thinking, but a matter of semantics - we don’t need to protect ourselves from a vacuum pump failure, we need to protect ourselves from any SINGLE failure (or dual failures if you like better odds - older airplanes were doing well to cover one failure deep). If you still rely on vacuum gyros, then an electric backup is a good idea - and you have to be ready to use it. Electric gyros? Backup alternator, a good battery, or a backup battery. Massive electrical bus short? How about a split-bus architecture that lets you kill the one making sparks? That covers airframe systems - what about the avionics themselves? (And yes, I recognize the biggest single point failure we have - the engine - but that’s the same for old or new ASEL’s….)

So lets say that you have an EFIS with a single AHRS and a separate autopilot with an independent attitude (or at least attitude rate) source. The EFIS goes belly up, the autopilot covers you until you get to VFR conditions. Single failure, safe operation - and no one is flying needle and ball! Dual AHRS and dual EFIS displays? One fails, you still have the other, and life is good - no special techniques required. Just fly like you are used to. I have the Pictorial Pilot in my airplane so that if I lose the EFIS entirely, I could use it as my T&B….but why would I hand fly partial panel - if it’s working, I’ll just engage the autopilot portion and let it keep us upright while I navigate! Now you can postulate as many failures as you want - there can be little doubt that with modern devices and architecture, we are at least as safe as older aircraft, and we have removed the most unreliable aspect from the system - not eh Vacuum pump, the pilot!

The point of all this? With new technology comes the need to change the way we think, and the way we train. Needle and Ball flying is rapidly becoming a thing of the past. Yes, if you get your instrument rating in an airplane without one, you shouldn’t be out flying an airplane that relies on that instrument as a backup. In periods of transition, we have to use discipline to stay within our training zone, just as it is not smart to set out in a tricycle gear airplane without transition training if you trained in tail draggers only. Or, for that matter, taking off in your new RV if all you had ever flown is a Cessna. Legal? Yes, but smart? No way - not without a chance to adapt to the speed and handling differences!

I haven’t seen a lot of modern glass cockpit jets that had a needle and ball, so it is a bit disingenuous to insist that everyone learn to fly them, just as learning to fly the ADF approach is rapidly becoming meaningless. As the Low Frequency Range went, so too will the NDB - and maybe even the VOR at some point in the future. Computer controlled automotive engines have replaced the need to know how to start your car with a manual choke, and redundant electronic gyros and displays will make the risky and difficult task of partial panel flying (as we know it it) just as obsolete before long.

The point of all this is that we need to adjust the way we think - not solution oriented, but problem oriented - Flying by Needle and Ball was a “solution” to the problem of single point failures. We need to look at (and accept) other, safer solutions as they present themselves if we are to enhance safety and further the utility of our airplanes.


05-10-2008, 05:26 PM
It is amazing to me how long it takes the FAA and ultimately the CFI's to adapt to the new technologies.

I can remember when carrying a GPS in the cabin got you labeled as "an "irresponsibly lazy" pilot.

05-10-2008, 08:13 PM
Needle, ball and airspeed was a concession to the industry long, long ago so the manufacturers could sell a certified IFR airplane at a reasonable cost.

Yes, we practice and show some proficiency at flying partial panel but it is always day VFR, in relatively smooth air and with a safety pilot. I have never read or heard of anyone actually saving the day on needle, ball and airspeed in hard IFR with any kind of turbulence. Conversely, there are many reports of accidents resulting from an AI failure at night and/or IFR. I know of one locally a few years back - a very nice Bonanza no more. One former Missouri governor also experienced it much to his family's regret.

In the beginning needle, ball and airspeed was inadequate. The concept remains inadequate and yes, it is indeed obsolete. As obsolete as the range approach.

Bob Axsom
05-10-2008, 08:42 PM
I pulled my turn coordinator when I needed a hole for my Pictorial Pilot. In my previous airplane I had a couple of vacuum pump failures and a few total electrical failures some in IMC. The autopilot is the best backup in my airplane even though it has its limitations. It is more interesting that you mention the low frequency radio range - I am surely one of the last guys alive that worked on one. As far as needle ball being obsolete - no I don't think so. The beauty of these independent standalone instruments is they do not go obsolete. They continue to function based on the physical forces and not someone's production line, everchanging microelectronics or software. Every piece of glass in your cockpit will be obsolete and the AI, DG and Turn Coordinator will still work and allow you to maintain control in IMC 20 years from now. But ... the reality is we like the sophisticated equipment and we are willing to accept future obsolescence in exchange for safety of flight, accuracy, convenience right now even though we have no clue how the system really does what it does.

Bob Axsom

05-10-2008, 08:54 PM
Every piece of glass in your cockpit will be obsolete and the AI, DG and Turn Coordinator will still work and allow you to maintain control in IMC 20 years from now.

Hi Bob,

I don't fully understand what you mean by this. I don't see much difference between a Dynon D10 and a AI+DG. It seems to me that I can use them similarly, and likely the Dynon (or similar) will last far longer than the spinning gyro in the AI.

05-10-2008, 09:04 PM

Hate to burst your bubble, but I have had two needle/ball/airspeed saves. One was modererate IFR in a single with a non-pilot in the right seat (everytime I nearly forget about that one my Dad reminds me about the "emergency" on the only IFR flight he flew with me). The other was hard IFR in moderate icing with moderate turbulence single pilot in a Cessna 310 after the left engine failed - the right vacuum pump failed once it wasn't receiving any help from the left pump. The boots were pneumatically powered off the vacuum system as well, so partial panel was only part of my problem on that one.

All that said, I think Paul's point is very valid in our environment. In my RV, I have two seperate electrical systems with independant batteries and alternators. My "no fail" avionics may be powered off either system (two different schemes - GRT systems use diodes and draw power off whichever system is operating, while radios and TruTrak ADI use three position power switches; OFF, Main Bus, or Essential Bus), and there is no provision to tie the busses. Pull-able breakers allow any system to be isolated from either bus. A standby battery provides tertiary power to the AHRS and main GRT display. This gives me what I consider an acceptable level of redundancy, and I believe the TruTrak ADI to be a much superior instrument to the traditional needle/ball/airspeed in an RV.


05-12-2008, 09:47 AM
...moderate icing with moderate turbulence single pilot in a Cessna 310 after the left engine failed - the right vacuum pump failed once it wasn't receiving any help from the left pump...

Dang, that kinda sounds like my ATP checkride, sans the icing. I did the ride in a C-310R on a bumpy summer day with Fed from the Lincoln, NE FSDO. He tells me to head to an NDB and expect holding. As we're nearing the beacon he slaps a couple of Post-It notes on the AI and HSI... so there I am, bouncing around a holding pattern with just the needle/ball and whiskey compass. Then he clears me for the NDB approach... and while on the procedure turn inbound he failed an engine. Oh boy, a single engine partial panel NDB approach on a bumpy day, what fun!

And how did the ride go? Yeah, I got a pink slip on that one. I kept it upright and right down the runway on the approach, but when I tried to level off at the MDA, the ship just wouldn't hold altitude and kept slowly sinking. Turns out I had approach flaps out and forgot to clean 'em up with the engine failure; on a hot day, single engine with some flap out, even a lightly loaded 310 won't maintain altitude.

I went back a week later and did the ride again. Same scenario, partial panel single engine NDB approach, but this time I got the flaps up. Yea, I passed.

05-12-2008, 01:37 PM
OK, here is a question that my raise the ire of the more experienced pilots in the room - is flying by needle, ball, and airspeed obsolete?

The traditional analog instruments are not obsolete, if only by virtue of the fact that out of the 200,000+ GA aircraft in existence, probably 90% of them have the older style panel.

Of course, if you have an RV-X and only plan on flying that airplane and it's got glass and you can fly it proficiently (including partial-panel, whatever that may look like in your ship), then there is no need to be able to fly with a turn coordinator, altimeter, and airspeed indicator, is there?

On the other hand, when I train students to fly IFR in glass airplanes like the SR22 and Columbia, I ensure they can fly a traditional six pack as well via some simulator training. There are several reasons for this: first, I want them to be a complete instrument pilot able to fly more than just an Avidyne or G1000. Second, I want them to understand the way analog instruments work since there are analog instruments even in those glass aircraft, and they have different failure modes and different scans than an AHRS-based system. Third, it's harder to go "back" to analog instruments than it is to go "forward" to glass panels if you're already a rated and experienced pilot, so I want the heavy lifting to be done while we're already doing the heavy lifting: during primary instrument training.

I disagree with those who feel instructors are anti-GPS, anti-glass, attached to older technology, or provide unrealistic failure modes for no good reason. I know none who have that attitude. On the other hand, we often turn those devices off or direct a student's focus elsewhere because it's necessary for training. If we don't push your workload to the breaking point, fail instruments and radios, etc. then we're not doing our job. Anyone can fly IFR when everything's working. But when you're on one engine or partial panel in the clouds, a passenger is airsick, you need a bathroom break, the fuel is getting low, it's night, and you're tired, that's not the time to find out how well you perform when stress is high. That's why we push you hard. If you ever have a bad day and come out the other side in one piece, you'll understand that.


05-12-2008, 02:44 PM
I don't mean to hijack Paul's thread but perhaps to ask that some of the light being shed on the topic be focused into a particular dark corner...

My aircraft is a little better than basic VFR, with Dynon D100 EFIS, moving map GPS, and analog airspeed, altimeter, VSI, whiskey compass and vacuum-operated (via a venturi) Turn&Bank. Obviously the analog pitot-static instruments are my backup to the Dynon. But where I'm concerned and need some guidance based on experience with the T&B.

You see, I picked up a nice vacuum-powered attitude indicator and have been toying with the idea that an attitude indicator would make a better backup instrument than a T&B. I'm sure there's some down-side to this plan that I'm not seeing, and as somebody who has either flown straight VFR with my head out the window, or hard IFR in fully integrated flight decks from Boeing and Airbus, I'm sure I'm missing something. When I look at the backup instruments in the heavies I see a standby attitude indicator. Why isn't my little airplane going to benefit from the same redundancy plan?

Thanks in advance for your patience in shedding light into this little corner of the debate.

05-12-2008, 05:23 PM
Paul, good question. I don't know the answer to whether or not needle/ball is obsolete.

I think one of the reasons the T&B or TC has hung around as long as they have is their established reliability. I think most would agree that if the horizon (efis or otherwise) is showing a bank and the T&B isn't showing a turn, it might be advisable to believe the simpler instrument (assuming it appears to be "alive" and responding to rudder inputs). The gyro is captured and only allowed a small amount of movement, so no such thing as tumbling, etc. My TC was howling with bad bearings yet still functioned just fine.

Paul, your comment that if the efis croaks, you'll just use the redundancy of the autopilot. However, what if the autopilot is flying when you see the efis indicating something amiss. Which one wins? We always need a third vote (and I know you have that in your plane Paul). With the classic vacuum AH and HI and electric T&B or TC, there is a set training regimen for what to do with mysterious indications (we don't have good data on how successful this is - only for when it isn't).

One potential large problem we are creating with our mostly one of a kind panels and architecture is for future owners/pilots of these airplanes. I see nothing but trouble there.... How to "train" the new pilot how to know what to believe? What is the proper sequence of detective work when something croaks? With the old six pack there is a known interaction.

It will be interesting...

05-12-2008, 08:26 PM
I agree that during instrument training some analog is necessary. For someone intending to make flying their profession, the first flying job should be in an airplane with steam gauges and no auto pilot. Get the basics drilled in first, then go to the "easier" glass. I've seen too many instances of guys with glass regional jet first job have difficulty with a DC9 or 727 while those coming from B1900s seldom have trouble stepping up to A320s. So back to the thread.....It seems to me that the "alternate power source back up" should give you as much info as possible. Electric attitude gyros used to be very pricey. With the reasonably priced electric attitude/direction gyros available why use an instrument that doesn't provide pitch info? I have also had a vacume pump failure in mostly smooth IMC (in a C182 one of the easiest aircraft to partial panel) and it was a non event. On a dark and stormy night I'd would rather have an ADI and autopilot. It does seem to me that to provide airline type redundency in the panel on an aircraft with one engine and prop and no deice capability may be lead one to expect an awful lot of the total system.

Old guy, CFI ATP, RV dreamer since my cousin let me fly his 4

05-12-2008, 08:52 PM
I'm a VFR only type pilot. I don't ever remember flying an airplane with a needle and ball. I probably did, I just don't remember seeing anything that looked like a "ball and needle". What the heck are they?;) Only a few hours of my 2,800 hours total time are in aircraft with engines so you need to cut me some slack on this one. I remember seeing artificial horizons on the panel in airplanes but that's not the same as a ball and needle right?

Most of my flying over the past 41 years has been in gliders. There are no minimum required instruments in gliders in general, it's specific to each model as listed in the Type Certificate Data Sheet. Typically that's just an airspeed, altimeter, magnetic compass and a variometer of some type. Heck, I rarely looked at those either. You fly a glider by feel. And look at the panel only to confirm what you ears, eyes and butt have already told you. A short piece of yarn taped to the nose was helpful in keeping the fuselage straight when in tight thermals though.:)

When I built the panel for my RV-8A, I included a "kind of artificial horizon" (ADI-Pilot-1) as part of the TruTrak system. And my Dynon FlightDek D-180 has an artificial horizon. But panel space is limited so what advantages would a ball and needle give me over my redundant artificial horizons? :confused: And what the heck are those things anyway?

Al Thomas
Wiring, messing with fiberglass and engine stuff