IFR Instrumentation - VSI's

[Skates97]

This came up in a different thread but I wanted to start a new thread rather than completely sidetrack that one. I thought that the VSI was required, but from looking through 91.205 at required instrumentation it is not. This brings up my question. I am just now getting into studying for my IFR written. If you don't have a VSI in the plane, how would you make sure you are meeting the minimum climb gradient?

[gacoon]

You cross check altitude change with seconds on clock.

[47U]

40 minutes ago, Skates97 said:

you are meeting the minimum climb gradient

Which is given as altitude gained over distance traveled, so a conversion to feet per minute is required depending upon your ground speed.

[Skates97]

10 minutes ago, 47U said:

Which is given as altitude gained over distance traveled, so a conversion to feet per minute is required depending upon your ground speed.

Yes, I understand that. They can't give it in feet per minute because that is dependent upon your speed, but I would challenge anyone to fly and keep track of it by altitude gained over distance traveled instead of doing the math and making sure they are climbing at xxx fpm. I was just surprised to see that you don't have to have a VSI for Part 91 IFR operations. Seems that a VSI while not required is extremely beneficial. 

[47U]

17 minutes ago, Skates97 said:

I was just surprised to see that you don't have to have a VSI for Part 91 IFR operations. Seems that a VSI while not required is extremely beneficial. 

No doubt as to the benefit of the VSI.  But, if you don’t have an alternate static source installed and your static ports have iced over, it’s the VSI glass that gets broken so that the altimeter and airspeed start working again (albeit, with some error factor).

[ArtVandelay]

Any GPS box can give you a climb rate. ATC will ask for “best” climb or descent rate, but I’ve never heard them ask for a specific value.

[Rwsavory]

Whether or not it’s required you need a VSI or equivalent to safely fly on instruments.  It’s a big pointer that tells you quickly whether you’re going up or down, and that’s important to know.

There was a comment in another thread about ditching the VSI and using the G5 instead.  I’ve been using the G5 for a couple months now, and the vertical speed indication is very small. A larger flat panel display would be needed, imho.  

[Hank]

57 minutes ago, Rwsavory said:

Whether or not it’s required you need a VSI or equivalent to safely fly on instruments.  It’s a big pointer that tells you quickly whether you’re going up or down, and that’s important to know.

There was a comment in another thread about ditching the VSI and using the G5 instead.  I’ve been using the G5 for a couple months now, and the vertical speed indication is very small. A larger flat panel display would be needed, imho.  

I really like my IVSI. No multi-second delay, no "where you were several seconds ago". Do any of the fancy new boxes do that? And which of the fancy new boxes shows the VSI all of the time instead of removing it when their programmer thinks you don't need it?

[EricJ]

6 hours ago, Rwsavory said:

Whether or not it’s required you need a VSI or equivalent to safely fly on instruments.  It’s a big pointer that tells you quickly whether you’re going up or down, and that’s important to know.

There was a comment in another thread about ditching the VSI and using the G5 instead.  I’ve been using the G5 for a couple months now, and the vertical speed indication is very small. A larger flat panel display would be needed, imho.  

Most VSIs, if they're not specifically IVSIs, have a lot of lag and the altimeter will indicate climb/descent more readily than the VSI will.

The VSI on the G5 should respond more quickly than a typical air-driven VSI, but I agree it could be more visible than it is.   If you know what you're looking for, though, and are looking specifically for it, it isn't that bad.

[vorlon1]

12 hours ago, ArtVandelay said:

Any GPS box can give you a climb rate. ATC will ask for “best” climb or descent rate, but I’ve never heard them ask for a specific value.

I see what you are getting at, but specifying a departure procedure would infer one... Just sayin'

[ArtVandelay]

I see what you are getting at, but specifying a departure procedure would infer one... Just sayin'

VSI still isn’t required, after all the DP specifies the minimum climb rate and hopefully you know this BEFORE you take off, since you know the climb rate required, you have the POH charts you can figure out if you can make minimum rate, the VSI isn’t going to help you other than tell you how badly screwed up.
GPS will tell you that, plus the added benefits of terrain warnings.
;-)


Tom

[vorlon1]

Just now, ArtVandelay said:

VSI still isn’t required, after all the DP specifies the minimum climb rate and hopefully you know this BEFORE you take off, since you know the climb rate required, you have the POH charts you can figure out if you can make minimum rate, the VSI isn’t going to help you other than tell you how badly screwed up.
GPS will tell you that, plus the added benefits of terrain warnings.
;-)


Tom

Thanks for making my point for me. Note I commented only about ATC asking for a specific value for climb rate... Not how to meet it or instrumentation involved.

[Skates97]

 

1 hour ago, EricJ said:

Most VSIs, if they're not specifically IVSIs, have a lot of lag and the altimeter will indicate climb/descent more readily than the VSI will.

The VSI on the G5 should respond more quickly than a typical air-driven VSI, but I agree it could be more visible than it is.   If you know what you're looking for, though, and are looking specifically for it, it isn't that bad.

I haven't had the G5's in for very long but do have quite a few hours behind them now. The VSI on the G5 works well for me and I look at it far more than the traditional VSI in the panel. Then again, before I had the G5's I would look at the Altimeter more than the VSI to hold altitude because of the lag in the VSI. If I had an IVSI like Hank maybe it would get more attention from me.

[jaylw314]

15 minutes ago, vorlon1 said:

Thanks for making my point for me. Note I commented only about ATC asking for a specific value for climb rate... Not how to meet it or instrumentation involved.

You referenced departure procedures, not just ATC.

Departure procedures only reference climb angle, not climb rate.  The terrain doesn't move and doesn't care how fast you're climbing.

The only necessary callout for climb rate with ATC is if you can't make 500 fpm.  I can't say I've ever had ATC ask me to climb or descend at a certain speed, other than faster than what I'm doing now.

[Hank]

1 hour ago, Skates97 said:

 

I haven't had the G5's in for very long but do have quite a few hours behind them now. The VSI on the G5 works well for me and I look at it far more than the traditional VSI in the panel. Then again, before I had the G5's I would look at the Altimeter more than the VSI to hold altitude because of the lag in the VSI. If I had an IVSI like Hank maybe it would get more attention from me.

I really like my IVSI, and reference it much more often than the altimeter. It tells me immediately when I start to drift, and when I've stopped it. Then pop it that far the other way and watch the altimeter so I know when to stop.

[Skates97]

To throw another wrench into this discussion, in the G5 installation manual it says that the VSI must be retained. If it is not a required instrument, why would it say that it must be retained?

[vorlon1]

1 hour ago, jaylw314 said:

Departure procedures only reference climb angle, not climb rate.  The terrain doesn't move and doesn't care how fast you're climbing.

The only necessary callout for climb rate with ATC is if you can't make 500 fpm.  I can't say I've ever had ATC ask me to climb or descend at a certain speed, other than faster than what I'm doing now.

it's more than that.  Here's a hint: for example, 310' per NM is a gradient. 

[jaylw314]

39 minutes ago, vorlon1 said:

it's more than that.  Here's a hint: for example, 310' per NM is a gradient. 

 

Um, thank you for making my point?

[jaylw314]

46 minutes ago, Skates97 said:

To throw another wrench into this discussion, in the G5 installation manual it says that the VSI must be retained. If it is not a required instrument, why would it say that it must be retained?

Wild.  I wonder if there are any aircraft whose TCDS requires the presence of a VSI?  Maybe aerobatic ones?  Anyone know?

[Skates97]

23 minutes ago, jaylw314 said:

Wild.  I wonder if there are any aircraft whose TCDS requires the presence of a VSI?  Maybe aerobatic ones?  Anyone know?

For part 125 operations, if a plane has a seating capacity of 20+ or payload of 6,000+ a VSI is required. I don't know enough about the planes in the AML for the G5 STC to know if any of them fall into that category. It also looks like a VSI is required for Part 135 IFR operations so maybe they put that in the installation to cover an instance where the aircraft it is being installed in requires it for the type of operations. In that case though I would think the wording would be different, something along the lines of "if a VSI is required by regulation/TCDS/etc..." 

STC - sa01818wi_08.pdf

[ArtVandelay]

To throw another wrench into this discussion, in the G5 installation manual it says that the VSI must be retained. If it is not a required instrument, why would it say that it must be retained?

And yet it can be the backup to all 6 if paired with a Garmin glass panel.
The above is a marketing position, nothing about the instrument itself.

[Jim Peace]

20 hours ago, ArtVandelay said:

ATC will ask for “best” climb or descent rate, but I’ve never heard them ask for a specific value.

They do all the time....at lease in jets....They may ask to give at least so many feet per minute etc....helps to have the VSI...especially an IVSI...

[carusoam]

The VSI provides such an important piece of information... all Mooneys get one.

It gets used going around the pattern... usually about twice...

That’s before going on long x-countries...

 

If the FAA doesn’t require planes to have it... this is probably a legal technical issue...

Somebody with a watch and an altimeter and is handy with their math and working memory skills... can do this in his head...

 

Most MSers can quote their T/O procedures on when to raise the gear... positive rate, up goes the gear...

The landing procedure... from level in the pattern... MP is about 16”... dropping 3” to 13” allows for a general descent of  about 300fpm... verify that on the VSI... then adjust 1” at a time for any variation...

The quality of the descent to landing gets defined by the VSI... stable approach will not be achieved descending 1kfpm...

The FARs are written by some technically intelligent and expert legal-ease writers... and get updated in waves by additional technically ept legal writers...

Don’t be surprised by interpreting what they wrote, or why they wrote that way...

Somebody was saving their life savings on a VSI... because they technically didn’t need one... if they were fast with their math, and their multi-tasking skills were brilliant!

 

Positive rate and 300fpm every time... more or less...  

As far as climbing in an NA Mooney on an IR flight plan... Push the throttle all the way in... see what you get.  Descending, pull the throttle back... see what you get...

PP thoughts only, IR’d but no where near current...

Best regards,

-a-

 

 

[carusoam]

On 11/1/2020 at 10:25 PM, Skates97 said:

This came up in a different thread but I wanted to start a new thread rather than completely sidetrack that one. I thought that the VSI was required, but from looking through 91.205 at required instrumentation it is not. This brings up my question. I am just now getting into studying for my IFR written. If you don't have a VSI in the plane, how would you make sure you are meeting the minimum climb gradient?

this is where the requirement for IFR flight shows the VSI... 

In the POH limitations section... the MEL.... 

check out the foot note that goes with that...   **** When required by the appropriate regulations... 

So... if you are a legal Eagle, and know what the ‘appropriate regulations’ are...

You may not need the device... in all other cases... it is listed in the MEL so you need it for this plane...

When is anybody going to ask to see your VSI?

I’m sorry sir, I’ll need to have representation prior to showing you my VSI...

I think we are going to need an aviation attorney to give an opinion on this technical legal issue... or the POH’s author...

Best regards,

-a-

[Hank]

6 hours ago, carusoam said:

The VSI provides such an important piece of information... all Mooneys get one.

It gets used going around the pattern... usually about twice...

That’s before going on long x-countries...

 

If the FAA doesn’t require planes to have it... this is probably a legal technical issue...

Somebody with a watch and an altimeter and is handy with their math and working memory skills... can do this in his head...

 

Most MSers can quote their T/O procedures on when to raise the gear... positive rate, up goes the gear...

The landing procedure... from level in the pattern... MP is about 16”... dropping 3” to 13” allows for a general descent of  about 300fpm... verify that on the VSI... then adjust 1” at a time for any variation...

The quality of the descent to landing gets defined by the VSI... stable approach will not be achieved descending 1kfpm...

The FARs are written by some technically intelligent and expert legal-ease writers... and get updated in waves by additional technically ept legal writers...

Don’t be surprised by interpreting what they wrote, or why they wrote that way...

Somebody was saving their life savings on a VSI... because they technically didn’t need one... if they were fast with their math, and their multi-tasking skills were brilliant!

 

Positive rate and 300fpm every time... more or less...  

As far as climbing in an NA Mooney on an IR flight plan... Push the throttle all the way in... see what you get.  Descending, pull the throttle back... see what you get...

PP thoughts only, IR’d but no where near current...

Best regards,

-a-

 

 

This is the only part I disagree with. Whether VFR or IFR, I just push the yoke for 500fpm and accept the speed I get.