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How do you ensure you meet a climb gradient in your RV?

jcarne

Well Known Member
Patron
Okay everyone, I have searched for a long time now and not finding much of what people do with their RVs in this category.

I'm getting ready for my instrument check ride soon and while I know my RV pretty well at this point and its climb rate at various density altitudes, I doubt the examiner is going to accept my word and why would he if the topic comes up?

I have slowly developed a climb performance spreadsheet over time (and during phase 1) but it has a lot of incomplete areas because wildly different than standard days or low pressure altitudes don't present themselves where I live.

I suppose a possible good method would be to use a Koch chart but with the RV I find it to be extremely conservative. Like absurdly conservative.

Anyone have some advice/experience here? Thanks!
 
A few thoughts.
1. Most examiners are content to test this part during the oral. Make sure you convert IAS to TAS to ground speed (watch out for tail winds, etc). Make sure you can find required climb gradients on the charts. Make sure you know the ‘standard’ (200’/nm if not published) climb gradient. (Rare in WY!)
2. For flying, explain that you use Vy (converted to TAS plus minus the wind to ground speed) and the rate of climb at Vy at various density altitudes (hopefully you have this data from phase 1 testing (but don’t overlook the effect of weight), knowing that this is not as good as Vx but that builds in your safety margin.).
3. There are very few departure procedures an RV cannot do, except the ones clearly designed for turbojets.
4. In many locations you can negotiate a ‘…climb over the airport in vfr conditions to xxxx feet before departing on course…’ type of clearance, if obstacle clearance is an issue.
 
A few thoughts.
1. Most examiners are content to test this part during the oral. Make sure you convert IAS to TAS to ground speed (watch out for tail winds, etc). Make sure you can find required climb gradients on the charts. Make sure you know the ‘standard’ (200’/nm if not published) climb gradient. (Rare in WY!)
2. For flying, explain that you use Vy (converted to TAS plus minus the wind to ground speed) and the rate of climb at Vy at various density altitudes (hopefully you have this data from phase 1 testing (but don’t overlook the effect of weight), knowing that this is not as good as Vx but that builds in your safety margin.).
3. There are very few departure procedures an RV cannot do, except the ones clearly designed for turbojets.
4. In many locations you can negotiate a ‘…climb over the airport in vfr conditions to xxxx feet before departing on course…’ type of clearance, if obstacle clearance is an issue.

Thanks Bob, your thoughts align with what I was thinking. Only tricky part is I don't have a complete climb performance chart for every pressure altitude I could be given. I guess for check ride purposes I will use the closest one on my chart as long as it is lower performance conditions than what I am calculating for. Otherwise a VCOA or not proceeding IFR would be my only options. I too have found that the RV has easily complied with all climb gradients so far (even out here in WY :)). I also realize that if I ever see a stupid high climb gradient like Aspen I don't think I will be wanting to proceed IFR anyways. lol
 
Thanks Bob, your thoughts align with what I was thinking. Only tricky part is I don't have a complete climb performance chart for every pressure altitude I could be given. I guess for check ride purposes I will use the closest one on my chart as long as it is lower performance conditions than what I am calculating for. Otherwise a VCOA or not proceeding IFR would be my only options. I too have found that the RV has easily complied with all climb gradients so far (even out here in WY :)). I also realize that if I ever see a stupid high climb gradient like Aspen I don't think I will be wanting to proceed IFR anyways. lol

I have not done testing at countless altitudes and temps. I use my baseline charts and apply adders from a Koch chart to help with varying density altitudes.

Also, find a time that kind of matches the standard and just do a fixed IAS climb (Vy) from SL to 10K and record the climb rate / FPM at each 1000' point and that will give you the data you need. Then use the Koch chart to account for hotter or colder temps.

Larry
 
Thanks for the replies guys. I think I have something that will work now involving my test data and a Koch chart.
 
If you have Garmin G3X you can put it in the data bar field:

CLG - Climb Gradient Current climb gradient (climb rate divided by
groundspeed) in percent.

CLM - Climb Gradient (ALT/NM) Current climb gradient (climb rate divided by
groundspeed) in altitude per nautical mile.
 
I conducted a climb test in my RV-7 at various altitudes, all the way up to 13,000 and determined a basic rule. I can climb at 1,000fpm up to and including 10,000ft DA.
 
If you have Garmin G3X you can put it in the data bar field:

CLG - Climb Gradient Current climb gradient (climb rate divided by
groundspeed) in percent.

CLM - Climb Gradient (ALT/NM) Current climb gradient (climb rate divided by
groundspeed) in altitude per nautical mile.

That is a super-cool feature.
 
That is a super-cool feature.

The GRT Hx can do something similar, but different: if you look up the location and altitude of the limiting obstacle, enter that data into the Hx, it will show a green arc before (good) or beyond (bad) that obstacle, where you’re projected to get to that altitude. But of course these are safety backups, not pre-flight planning tools, which the OP asked about.
 
The GRT Hx can do something similar, but different: if you look up the location and altitude of the limiting obstacle, enter that data into the Hx, it will show a green arc before (good) or beyond (bad) that obstacle, where you’re projected to get to that altitude. But of course these are safety backups, not pre-flight planning tools, which the OP asked about.
Same for the Dynon, but that requires you to be airborne to see the altitude intercept arc, it's not available in the planning stage, unless I've misread your post (always possible!)

Probably the easiest way to prove or test your climb gradient would be to climb the altitude of the highest runway in the US and then simulate an after-takeoff climb. If you can maintain 500FPM at, say, 80 knots GS at a DA in the low teens you should be able to "prove" sufficient climb rate to exceed the climb gradient at any DA below that at which you tested (apply whatever figure you require for your own airplane of course).
 
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