primary inst while on Glide slope?

[saviboy]

what is primary inst. when on the glideslope?
thanks

 

[mike1mc]

I was taught to use the VSI and DG. Nials those two and you'll always keep the needles pegged. This also keeps you from chaisng the LOC and GS. I'm sure everyone has their own opinion.

 

[pilotman2105]

I was taught to use the VSI and DG. Nials those two and you'll always keep the needles pegged. This also keeps you from chaisng the LOC and GS. I'm sure everyone has their own opinion.

Provided your airspeed doesn't change, you are correct.

 

[falcon20driver]

It's all about control and performance, forget that primary and secondary **CENSORED****CENSORED****CENSORED****CENSORED**.

Set an attitude with the attitude indicator, trim, crosscheck and adjust.

For the glide set your attitude and use the VSI to see what performance you're getting, if you're high reset your attitude for a greater descent rate.

I use the airspeed as my performance gauge for power on the ILS.

 

[mmmdonut]

Provided your airspeed doesn't change, you are correct.

Ground speed.

 

[pilotman2105]

Ground speed.

(And what the hell is with the "The message you have entered is too short. Please lengthen your message to at least 5 characters?" So much for conserving bandwidth with my wink instead of this long drawn out question.)

 

[FlyinTim]

I personally believe that all this Primary stuff is BS...do what feels right...keep your scan but do your own thing...

 

[Tinstaafl]

I disagree, FlyinTim.

I've spent more hours than I can recall watching students try to have some amount of stable & precise flight controlling the a/c in response to either LOC/GS indications or VSI (non-IVSI)/ASI/ALT. There IS a difference in effect if the pilot's inputs are held until a performance or navigation display responds vs. a pilot's input against the AI/AH then waits for noticeable change, assess the rate of response in relation to the nav/performance instruments & reiterates.

So, when someone asks about primary instruments my first question is 'In relation to what? Control of the aircraft or measurement of performance WRT to a desired flight path?'

If control is the point then the AI/AH + power indicator(s) are primary. If measurement WRT to flight path then one could argue that the primary instrument is the performance instrument that most readily defines the desired plane(s) of the flight path however this only measures performance not control.

 

[minitour]

If you're looking to maintain the centerline of the LOC and GS, wouldn't your primary instrument be the HSI or VOR/LOC/GS?

Using your nav instruments keeps your needles centered...everything else is supporting?

IE.
LOC/GS = Primary for Bank and Pitch
ASI = Primary for Power

DG/AI = Supporting for Bank
ALT/VSI/AI = Supporting for Pitch
Tach/MAP Gage = Supporting for Power

Perhaps I'm making this too simple...to me what makes sense is on an ILS you maintain the GS and LOC in the center. To do that, you "fly the needles" all the way to DH.

Just an opinion....probably wrong...

Eyeore has left the building...

-mini

 

[satpak77]

not be be a wise-a$$, but my primary instrument on the ILS IS the localizor and GS needles

follow those and everything else works out, hell you even are at VREF at 50 feet and land at the 1000 foot markings

can't ask for much more than that

(above is based on airplane being properyly configured per POH/etc during approach)

 

[Lead Sled]

not be be a wise-a$$, but my primary instrument on the ILS IS the localizor and GS needles

follow those and everything else works out, hell you even are at VREF at 50 feet and land at the 1000 foot markings

can't ask for much more than that

(above is based on airplane being properyly configured per POH/etc during approach)

I was going to say that the primary instrument on the ILS is the flight director.

'Sled

 

[Tinstaafl]

It's a form of linked chain concept.

If you, say, pitch the a/c to correct a GS error using the GS to tell you when to stop pitching then you'll overcorrect, resulting in flying through the GS and a mirror image of the problem. This yo-yo-ing results in the GS being seen -momentarilly - as the a/c passes from one side to another. As a/c speeds, mass & inertia increase, and proximity to the transmitter decreases then the pilot responses will not be adequate to constrain the flight path within the required tolerances.

So, the next step back from the direct reading instrument (the GS display), is to establish a nominal rate of descent for the rate of closure that will match the GS angle. At best the a/c will exactly parallel the GS (if the descent started whilst on the GS), at worst the descent will diverge at a rate inversely proportional to the distance from the transmitter. Of course this assumes the ROD is exactly correct. If the descent rate is incorrect then it will result in either closing with the GS (yay!) or diverging from it (boo, hiss).

Trouble is that pitching to establish a descent rate by reference to a normal VSI results in a similar GS display ie yo-yo-ing.

What next? Use the AI/AH to set a constant pitch angle. If power is unchanged then ROD is roughly linearly proportional to pitch attitude, at least close enough over small changes to be useful. Now the key becomes 'check the GP to determine location WRT to the GS, check VSI to determine ROD WRT a previously calculated approx. 'ideal' ROD --> adjust pitch attitude by a small amount WRT to the AI/AH & wait for a stabilised (or nearly stabilised) new ROD in the appropriate sense --> wait for change of position WRT to the GS to be indicated on the GS display. If the rate of change is insufficient then reiterate.

NB: At some point in this process will be found a pitch attitude that very nearly 'freezes' the GS needle. Remember that attitude for when the GS is eventually regained then use it as the subsequent baseline reference point.

This results in a far more stable & controlled GS than the other scenarios I mentioned.

The principle in the above GS example is no different to establishing a CDI intercept. I don't think anyone would advocate rolling the a/c until they saw the CDI move? Or, one step back from that, roll the a/c until they saw the HDG reach the desired point? Try that a 180deg required HDG change... . Instead we all roll the a/c by referencing the AoB on the AI/AH, holding the desired AoB while the a/c turns, then holding the new heading while waiting for the CDI to move etc.

So... in my view the AI/AH is the primary instrument(s) along with power & the ball.
Sorry if this gets a bit basic, but I found it difficult to explain my point without resorting to first principles.

 

[100LL... Again!]

The LOC and GS capture lights on autopilot panel

 

[nosehair]

If you're looking to maintain the centerline of the LOC and GS, wouldn't your primary instrument be the HSI or VOR/LOC/GS?

Using your nav instruments keeps your needles centered...everything else is supporting?

IE.
LOC/GS = Primary for Bank and Pitch
ASI = Primary for Power

DG/AI = Supporting for Bank
ALT/VSI/AI = Supporting for Pitch
Tach/MAP Gage = Supporting for Power

Perhaps I'm making this too simple...to me what makes sense is on an ILS you maintain the GS and LOC in the center. To do that, you "fly the needles" all the way to DH.



-mini

mini has it!
When this is practiced, the initial overcontrolling will eventually stop. You will learn to percieve the slightest movement of the needles and make an ever-so-slight control input to correct so that the needles don't get even a dot away.
The trouble with setting an attitude and power setting and don't chase the needles is, that it works fine with little or no wind or turbulance. But with strong crosswinds or large vertical movements, as in thunderstorms, the "primary instrument" technique will always work. Setting an attitude won't.

 

[Vandal]

ADI, crosscheck VSI and airspeed.