VSI or altimeter for pitch

DesertNomad

DesertNomad

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DesertNomad
My CFII has me flying approaches and holds, but we have not talked too much about a scan and what instruments I should be watching as primary and secondary. He has about 16,000 hours and has flown everything from J3 Cubs to Embraer jets.

Most books say that VSI is primary for pitch and the altimeter is secondary. My CFII says the opposite. I feel a bit overwhelmed and although I am able to fly an ILS pretty well, my scan is done without really any training or in depth discussion.

Thoughts?
 
In level flight, altimeter is primary.

VSI is primary in a rate climb or descent.

Airspeed is primary in a constant airspeed climb or descent.

All of this should be in the Instrument Flying Handbook.
 
On an ILS, keeping a steady rate of decent on the VSI is golden, 5-600 for most stuff works well.
 
In a descent, for me:
  • VSI and attitude indicator are the most useful instruments for pitch. The VSI gives a more sensitive indication. Depending on your particular aircraft's airspeed, -500 fpm for the vertical speed is probably about what you want, for the purpose of descending on the desired glideslope, in a small plane.
  • Altimeter is useful mainly for determining when to level out, to avoid busting altitude. I don't see how watching the altimeter unwind could be as good as the VSI, for adjusting your pitch to attain a desired glideslope.
 
The altimeter is primary for level flight (including turns). Otherwise, usually not.

I think you'll discover that there is a logic to this, and some variability. If you're holding constant altitude, the altimeter is primary. If you're holding constant heading, the DG is primary. If you're changing things, the corresponding rate becomes primary (TC for turns, ASI for constant airspeed climbs/descents, VSI for constant rate climbs/descents), and the AI is primary for transitions.
 
DesertNomad said:
Most books say that VSI is primary for pitch and the altimeter is secondary. My CFII says the opposite. I feel a bit overwhelmed and although I am able to fly an ILS pretty well, my scan is done without really any training or in depth discussion.

Thoughts?
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You might want to re-read some of those books...primary and supporting instruments vary depending behave of flight.
 
The VSI is a little more sensitive to a change in pitch than the other instruments, thus it's your primary go to instrument to see if you have pitched up or down when you really desire level flight.

Page 106 of the Instrument Flying Handbook:

"The pointer indication in a VSI lags a few seconds behind the actual change in pressure. However, it is more sensitive than an altimeter and is useful in alerting the pilot of an upward or downward trend, thereby helping maintain a constant altitude."
​
Chapter 6 of the IFH has more info on the topic under discussion.

And James has it right about knowing your pitch, power, performance numbers to hit a steady 500fpm descent on the ILS each and every time. One that condition is achieved, keeping the needles bullseyed is a simpler task.
 
Thanks guys. It does not help that it is summer in Reno with lots of thermals and bumps. My last instrument flight was in December.... then my plane broke on January 2nd and I didn't get it back until the end of February, whereupon I was caught up in work until my Cuba trip. So I am essentially starting over. I was only 7 hours into it when the plane broke.
 
James331 said:
On an ILS, keeping a steady rate of decent on the VSI is golden, 5-600 for most stuff works well.
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Ground speed times five or GS/2 X 10 for a 3 degree glide slope. I'm a big fan of flying the VSI. Works great for PARs.
 
Also no one has mentioned it but since you're likely to be wanting to fly it at a relatively constant airspeed, just setting the correct, known, power setting for the descent rate you want is the easiest way to get nearly exactly what you want with almost zero brain damage.

Gear should already be down, but it's your second place to check it, set power, and unless you have a tailwind, you're going to ride the glideslope just fine. Confirm with VSI and airspeed indicator and don't leave the alrimeter out of your scan -- now it's controlling for the missed unless get so far out of whack on the CDI that you have to call it off. Also don't forget your AI, it's always there to get a look at what angle is working perfectly and if you left the power alone, you can always pitch back to that too.

You'll get used to it. You really use all of the instruments, not just the primary/supporting thing. That's just a technique to know where to kinda look first. If your scan is moving fast enough and properly it's just a short pause for the eyeballs.

Get em moving again. Instruments fail. ;) (Instructor will have a ball with you if you like to fixate on one or two instruments... If you're hair starting approaches your instructor hasn't started "killing" you yet. Don't worry, you'll be dead soon. Heh.)
 
It was a challenge today in the wind and bumps. Plus ATC called off all three approach attempts and gave us vectors. The first was for a non-emergency medical flight and the others were for departing and arriving Southwest flights. The ILS was going well until they had me loop way back to the right and fly out to the VOR... then vector me past it. Yes, I was all over the sky for 1.8 hours. Quite a frustrating day.

Screen_Shot_2016_07_11_at_1_52_04_PM.png
 
RNO is a pretty gusty place to be trying to do anything precise this time of year. While that much is a given on a summer afternoon, over the last few days, it has been just as bad in the AM. Good on you for toughing it out though! As an aside, where is your home field?
 
35 AoA said:
RNO is a pretty gusty place to be trying to do anything precise this time of year. While that much is a given on a summer afternoon, over the last few days, it has been just as bad in the AM. Good on you for toughing it out though! As an aside, where is your home field?
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Reno is my home field. It was quite bumpy and gusty today - I had to hold 20-30 degrees of correction to maintain a course and even then it was just all over the place. Idle throttle and climbing 1000fpm with the nose pointed down makes things tough... triple so when under the hood. I flew from about 9:30am to 11:30am today. I can't imagine trying to do this in the afternoon. Today was the coolest day we will have all week.
 
Yeah, I'd say most of my last 10 landings out in fallon have been in at least a 10 degree crab at touchdown……..it has been work to get the old bird on deck as of late.
 
I just flew 8,000 miles to Cuba and back and landed at 35 different airports. The landing at Reno on the return was by far the most challenging.
 
DesertNomad said:
My CFII has me flying approaches and holds, but we have not talked too much about a scan and what instruments I should be watching as primary and secondary. He has about 16,000 hours and has flown everything from J3 Cubs to Embraer jets.

Most books say that VSI is primary for pitch and the altimeter is secondary. My CFII says the opposite. I feel a bit overwhelmed and although I am able to fly an ILS pretty well, my scan is done without really any training or in depth discussion.

Thoughts?
Click to expand...

FYI, the FAA has removed all primary/secondary questions from the knowledge exam. No effect on actually flying, of course.

Bob Gardner
 
bobmrg said:
FYI, the FAA has removed all primary/secondary questions from the knowledge exam. No effect on actually flying, of course.

Bob Gardner
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Bob, do you happen to know why they did that? Glass panels, maybe?
 
MAKG1 said:
Glass panels aren't any different. They just have the instruments in different places.
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I know that.

But scanning is a different experience with glass because you can simultaneously see at least two things.

For example, I can see both the VSI and horizon simultaneously without moving my eyes at all.

I can almost watch three things simultaneously, alternating between altitude and VSI with only the tiniest of eye movement while constantly seeing the horizon.

The idea of primary and secondary is crucially important when you can see only one thing at a time. I'm less sure of its importance when you can see two or three things at a time. That's why I am asking about the elimination of exam questions re primary/secondary.
 
NoHeat said:
I know that.

But scanning is a different experience with glass because you can simultaneously see at least two things.

For example, I can see both the VSI and horizon simultaneously without moving my eyes at all.

I can almost watch three things simultaneously, alternating between altitude and VSI with only the tiniest of eye movement while constantly seeing the horizon.

The idea of primary and secondary is crucially important when you can see only one thing at a time. I'm less sure of its importance when you can see two or three things at a time. That's why I am asking about the elimination of exam questions re primary/secondary.
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If your AHRS fails, you damn well had better know when your standby instruments are primary and when they aren't. No different.
 
MAKG1 said:
If your AHRS fails, you damn well had better know when your standby instruments are primary and when they aren't. No different.
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Ah, so are you saying that the idea of primary/secondary is important with glass, but due to the redundancy provided by backup instruments in a glass cockpit, the choice of a particular secondary instrument is not the same, as compared to a six-pack cockpit?

I'm glad to hear your thoughts, even though they don't address my question to Bob re. the FAA's thinking when it eliminated the questions.
 
NoHeat said:
Ah, so are you saying that the idea of primary/secondary is important with glass, but due to the redundancy provided by backup instruments in a glass cockpit, the choice of a particular secondary instrument is not the same, as compared to a six-pack cockpit?

I'm glad to hear your thoughts, even though they don't address my question to Bob re. the FAA's thinking when it eliminated the questions.
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No, you need the "six pack" concept when you are using the standby instruments. The scan geometry is quite different, but you still need to know the AI is primary for attitude changes, altimeter and compass for straight and level, and so on.

You really need to know it anyway. The difference you're noting is that the scan can be simplified. The instruments are all the same, as are the primary/supporting roles.
 
denverpilot said:
Also no one has mentioned it but since you're likely to be wanting to fly it at a relatively constant airspeed, just setting the correct, known, power setting for the descent rate you want is the easiest way to get nearly exactly what you want with almost zero brain damage.
Click to expand...

That is when approaches started getting easy for me. Once I had the power settings figured out, and had the aircraft trimmed properly, flying glideslopes got very easy. Usually don't even have to reference the VSI.
 
bobmrg said:
FYI, the FAA has removed all primary/secondary questions from the knowledge exam. No effect on actually flying, of course.

Bob Gardner
Click to expand...

From the Private and Instrument. Not from the FIA or FII yet, at least not when I took them. Still there.
 
Sportys just updated their Instrument Study Buddy, but it still had these questions. Is there a good source for which sort of questions are gone? I know the ADF/NDB stuff is no longer there (thank goodness!).
 
"Primary/Supporting" isn't a scan pattern...it's instrument interpretation. Whether you're steam or glass, the altimeter always gives you the most direct information to ensure that you're complying with your clearance of, say, "maintain 4000", so the altimeter is primary in this instance. Vertical speed, attitude, and potentially airspeed all give you information that can help you decide if your altimeter is or isn't working, so they're supporting instruments. Whatever scan pattern you use should allow you to correctly interpret the instruments.

For that matter, "Control/Performance" isn't a scan pattern, either...nor is it instrument interpretation. It's aircraft control. You establish a pitch and power setting using your Control instruments (Attitude & Tach, for example), and then verify that it works using your Performance instruments...in this case, your Altimeter would be the primary performance instrument and VSI, Attitude, & maybe airspeed would be your supporting performance instruments. Again, whatever scan pattern you use needs to allow you to correctly use and interpret the instruments.
 
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