What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

200 ktas plus RV

Adriaan Kleyn

I'm New Here
I am new to RV's . I want ro buildt a aircraft that is can fly 200 kts plus, but it must be a RV. I am thinking of a RV8 with a IO 390. Is that realistic ? I understand that a RV8 with the bigger engine is nose heavy, is that a concern. I am not into aerobatics but want a fast aircraft for x country. My thinking for the RV8 is because I am 6ft5 and doesn't fit comfortably into the RV7 . I need some real life experience concerning this matter.
 
An IO-390 won't do it unless you turboed it and flew high. Be aware of the relatively low Vne of the Van's designs compared to something like a Glasair or Lancair.

You probably shouldn't be probing these speeds in an RV unless you modified and tested it to somewhat above these speeds.

We've had a couple of turbo Subaru RV7s push through 200KTAS rather easily at rather low power settings so it's not hard to do but you want to do it safely.

Hitting some rough air at these speeds could put some extra serious loads on the airframe.

A Rocket might be more suitable for what you want to do.
 
Ross is right on. The Vne for the RV's is determined by True Airspeed for flutter prevention reasons (all this has been hashed out many times, and is the factory position), and for the -8, it is 200 knots. So if you want to cruise at that speed, you'd have absolutely no margin - not a good place to be, becasue if you DO find an engine that will pull the -8 at that speed, you'll frequently be flying over the flutter limit.

Look at Rockets (both Harmon's and F1's- and ask how they have tested their airframes for flutter.
 
Ok what is a realistic speed for a RV8 with a IO 390?

The published numbers found on Vans website.

Speed - Solo Weight
Top Speed 206 mph 214 mph 222 mph
Cruise [75% @ 8000 ft] 197 mph 204 mph 212 mph
Cruise [55% @ 8000 ft] 175 mph 182 mph 189 mph
Stall Speed 51 mph 51 mph 51 mph

Speed - Gross Weight
Top Speed 205 mph 213 mph 221 mph
Cruise [75% @ 8000 ft] 195 mph 203 mph 210 mph
Cruise [55% @ 8000 ft] 173 mph 180 mph 187 mph
Stall Speed 58 mph 58 mph 58 mph
 
The published numbers found on Vans website.

Speed - Solo Weight
Top Speed 206 mph 214 mph 222 mph
Cruise [75% @ 8000 ft] 197 mph 204 mph 212 mph
Cruise [55% @ 8000 ft] 175 mph 182 mph 189 mph
Stall Speed 51 mph 51 mph 51 mph

Speed - Gross Weight
Top Speed 205 mph 213 mph 221 mph
Cruise [75% @ 8000 ft] 195 mph 203 mph 210 mph
Cruise [55% @ 8000 ft] 173 mph 180 mph 187 mph
Stall Speed 58 mph 58 mph 58 mph

More power will significantly improve your ROC but won't add a great deal to your cruise speed. Check out the numbers on Van's site for the different engines.
 
More power will significantly improve your ROC but won't add a great deal to your cruise speed. Check out the numbers on Van's site for the different engines.
Yep.
A good rule of thumb for high speed cruise is speed is proportional to the cube root of power, all other things held constant. E.g., a 30% increase in power will give you about a 10% increase in speed.
 
Yep.
A good rule of thumb for high speed cruise is speed is proportional to the cube root of power, all other things held constant. E.g., a 30% increase in power will give you about a 10% increase in speed.
Cube Root of 30 is 3.10723250595 for a 3% increase.
 
I built a fast RV8, IO390, James cowling, extended hub CS BA prop, rocket style turtle deck.

I could run at 200 ktas down low wide open. Posted 227 mph in a closed course SARL race.

As several postings pointed out, 200kts is VNE for a RV8...although I did enjoy 185+ cruise speeds, at 200 and above, you will be a test pilot.
 
Agreed!

Your requirements dictate a Rocket.

If you can get to 200KTAS, you will be high, and you still have to come down. This is where the 240KTAS Vne of the Rocket can help keep the parts attached.

Caveat: you cannot use the 200KTAS cruise power setting in descent, even with a Rocket.

The plastic candidates that fit into this performance requirement are numerous..but the mission profile will change dramatically: no sod field landings for one..

Carry on!
Mark
 
Cube Root of 30 is 3.10723250595 for a 3% increase.


The cube root of 1.3 is 1.091, i.e a 9.1% increase. It's easier to increase speed with an efficient prop, aerodynamic cleanup and lighter weight. I see about 211 KTAS at 8500' WOT in my HR-II but I usually cruise at 180 KTAS at 10 GPH Unless it's a long trip.

Question.... if you have to travel so fast to save a few minutes getting there, why are you spending thousands of hours building? Just sayin'.
 
Last edited:
I am new to RV's . I want ro buildt a aircraft that is can fly 200 kts plus, but it must be a RV. I am thinking of a RV8 with a IO 390. Is that realistic ? I understand that a RV8 with the bigger engine is nose heavy, is that a concern. I am not into aerobatics but want a fast aircraft for x country. My thinking for the RV8 is because I am 6ft5 and doesn't fit comfortably into the RV7 . I need some real life experience concerning this matter.

Lets say you have an RV8 that does 175-180ktas. On a 400nm trip, a 200ktas airplane would save you about 15-20 minutes. Half that for a 200nm trip. That's almost negligible. In the grand scheme of driving to the airport, preflighting, pushing it out, refueling if you need to, starting, taxiing, flying, landing, taxiing, parking, tying down, refueling, getting transpo to where you need to go, etc., 10-20 minutes of extra time in the air is almost nil, especially when the cost of getting over the 200ktas cruise mark is so high in the way of motors, mods, and lack of flying examples out there relative to stock RVs. If you can get your hands on a rocket and have the funds for it (and increased fuel and insurance), then that's your best bet. Otherwise a clean IO360/390 -8 is probably your best bet, taking a (IMO) negligible hit to enroute/climb times.
 
200 knts

You need to think about fuel too. My -8 has tip tanks (60 gal total), so it can do 1000nm legs with IFR reserves in a little less than 6 hrs. Your IO-390 will be a little faster but with no increase in fuel load over a stock (42gal) RV and I'm pretty sure I'll beat you home (if my bladder survives anyway!). The extra speed really helps on long legs, but you have to have the fuel capacity and then your -8 becomes a one place bird. I keep thinking that a Lancair 4P is what I really need, just gotta rob a bank. In the meantime, my -8 has been to both coasts and gets me where I need to go faster than the airlines within a 1000nm circle, albeit it is significantly less weather capable!
 
You need to take the cube root of the power factor 1.3 which is 1.091, so actually a 9% speed increase assuming drag coefficient is constant.

Put simply in mathematical terms:

(Vnew/Vold) = (HPnew/HPold)^(1/3)

all other factors being unchanged (like Cd).

It takes a lot of additional power to get a little bit of additional speed.
 
Back
Top