Nitrous Oxide for take off??

[Capt.Crash'n'Burn]

Another stupid question, I'm sure I'm about to be bombarded with reasons why N2O is a bad idea for air cooled engines.

Could nitrous, under the right circumstances, be used to increase MTW of an airplane?


(god! when I actually get my hands on a Lycoming, imagine the carnage!)

 

[gismo]

Another stupid question, I'm sure I'm about to be bombarded with reasons why N2O is a bad idea for air cooled engines.

Could nitrous, under the right circumstances, be used to increase MTW of an airplane?


(god! when I actually get my hands on a Lycoming, imagine the carnage!)

Well, there's the whole certification thing.

While not exactly boosting MTOW (which BTW can be limited by other things than takeoff power), I once had the notion that NOX might be useful to restore sea level power to one engine on a twin if the other failed during takeoff at high DA. Seems like that would be relatively easy to certify (i.e. it would only take 10 years and a million bucks) since you wouldn't be increasing the max rated HP.

 

[Henning]

Another stupid question, I'm sure I'm about to be bombarded with reasons why N2O is a bad idea for air cooled engines.

Could nitrous, under the right circumstances, be used to increase MTW of an airplane?


(god! when I actually get my hands on a Lycoming, imagine the carnage!)

Well, nothing particularly wrong with using an NOS type fuel supplementer, Pushy Galore was on the bottle when she set her records, although IIRC that's a Continental....

As for increasing MGTW, there's more involved than just power, there are also multiple structural load issues not the least of being tires and tubes, then there's side loading on the gear, spars, spar connectors, fuselage load bearing ability....

 

[Capt. Geoffrey Thorpe]

Another stupid question, I'm sure I'm about to be bombarded with reasons why N2O is a bad idea for air cooled engines.

Could nitrous, under the right circumstances, be used to increase MTW of an airplane?

Nitrous is popular on air cooled motor cycles.

Wouldn't do much for TBO, but if that's not a problem (and you are operating in the experimental catagory) it would be one way to get of the runway faster.

How much it would help with just gross weight in general - that's a harder question - you wouldn't probably want to be running nitrous for the whole time it takes to climb to altitude.

 

[Ted]

Well, there's the whole certification thing.

While not exactly boosting MTOW (which BTW can be limited by other things than takeoff power), I once had the notion that NOX might be useful to restore sea level power to one engine on a twin if the other failed during takeoff at high DA. Seems like that would be relatively easy to certify (i.e. it would only take 10 years and a million bucks) since you wouldn't be increasing the max rated HP.

Seems to me that turbochargers are a much easier solution and provide other benefits.

 

[nyoung]

There was an article in a recent (2-3 months old) Sport Aviation about the STOL competition in Valdez, Alaska. One of the competitors (Wayne Mackey) was flying an aircraft called a Stolquest SQ2 (looks a bit like a Supercub), and was using nitrous for an additional 70hp on takeoff, so it certainly can be done. I have no idea about longevity concerns, but suspect that anything that adds that kind of power isn't going to help making TBO.

There is a an interesting interview/video of Wayne and the SQ2 at this link.
http://supercub.com/

 

[iflyforfun]

If we're not going to worry about certification - think going experimental - and you just want a boost on take-off or in an emergency, I'd go this route:
http://www.tecaeromex.com/ingles/peroxidoi.html

<day dream on>
~200 HP, fits in the palm of your hand, cool running and can be run for many minutes with fuel consumption in the range of a turboprop ... strap one on each wing mounted to reinforced spar and you've got yourself a VTOL :wink2:
<day dream off>

 

[gismo]

Seems to me that turbochargers are a much easier solution and provide other benefits.

Easier? I don't think so. A NOS setup is pretty simple. But the biggest difference is that the turbos would be useful in other scenarios besides an engine failure with high DA.

 

[Ted]

Easier? I don't think so. A NOS setup is pretty simple. But the biggest difference is that the turbos would be useful in other scenarios besides an engine failure with high DA.

I think it depends on how you do it. Nitrous systems (built by NOS or any other company) do tend to be pretty simple as far as hardware is concerned, but they can have various installation issues, especially getting the fueling correct. Turbocharger installations may be more complicated, but I'd still view as more straightforward.

 

[Henning]

I think it depends on how you do it. Nitrous systems (built by NOS or any other company) do tend to be pretty simple as far as hardware is concerned, but they can have various installation issues, especially getting the fueling correct. Turbocharger installations may be more complicated, but I'd still view as more straightforward.

I've never had an install issue putting an engine on the bottle tat took more than 1/2 an hour to overcome. I've put quite a few turbo engines on the bottle to overcome turbo lag for coming out of the hole and getting up on the step.

 

[Ted]

I've never had an install issue putting an engine on the bottle tat took more than 1/2 an hour to overcome. I've put quite a few turbo engines on the bottle to overcome turbo lag for coming out of the hole and getting up on the step.

You probably had better kits that were more scienced out and/or were just better at it. At my shop we put a few nitrous kits on the V12s and, while the engines responded well to it (especially coming with 11.5:1 compression out of the box), there weren't any readily available systems for them. That meant we had to put something together ourselves from components and, since we didn't do it all that frequently, it typically had problems. My concern is more that the problems may not be observable until the thing explodes.

A little 50 shot on a turbo car definitely does help get rid of the turbo lag, too.

 

[Doggtyred]

One of the rotary engined homebuilt crowd has an amphib and uses Nox for takeoff only.. Mainly to quickly get on the step and airborne.

As another poster iterated, NOX is simpler and easier than a turbo.. you dont have the heat, exhaust, shielding, turbo cooling and turbo lubrication issues to deal with. But NOX is a limited supply... its also not typically available at most fields so.. have to plan ahead for its use.

 

[RotorAndWing]

Back years ago when I was flying the SA-227's (Metroliner) we had alcohol/water injection for takeoff. Bring the engines up to about 80% and flip a switch, it was like going into afterburn. At about 1000' switch it off and the plane decelerated. It was a great system for heavy/hot takeoffs. Sprayed the mixture into the intakes and lowered the air density tremendously.

The huge old radial engines use to have a system of water injection for the same purpose. http://en.wikipedia.org/wiki/Water_injection_(engines)

 

[Anthony]

The ME-109 used a Nitrous Oxide system at times. That belly tank that was under the fuselage didn't always hold fuel, sometimes it held NOX. Yeah, this was 1940's.

 

[Capt.Crash'n'Burn]

If we're not going to worry about certification - think going experimental - and you just want a boost on take-off or in an emergency, I'd go this route:

That leads me to another question. If you had a certified aircraft, could you "de-certify" it and have it re-classified as an Experimental aircraft??

Like, for example, if you had an Aztec, took out the IO-540's and replaced them with IO-360's to increase range, and then used nitrous to help get your full 1800 lb payload into the air, then used the lower fuel burn rate of the 360 to get you further downrange.

Or am I just smoking crack??

 

[Capt.Crash'n'Burn]

Back years ago when I was flying the SA-227's (Metroliner) we had alcohol/water injection for takeoff. Bring the engines up to about 80% and flip a switch, it was like going into afterburn. At about 1000' switch it off and the plane decelerated. It was a great system for heavy/hot takeoffs. Sprayed the mixture into the intakes and lowered the air density tremendously.

The huge old radial engines use to have a system of water injection for the same purpose. http://en.wikipedia.org/wiki/Water_injection_(engines)

I was thinking, after I posted this, that water/alcohol might be a better choice since it doesn't raise engine temps quite as much.

 

[gismo]

That leads me to another question. If you had a certified aircraft, could you "de-certify" it and have it re-classified as an Experimental aircraft?

That doesn't accomplish what I believe you're thinking it would. There are many different "experimental" classifications and each comes with different rules and restrictions. I believe you're thinking about the "Amateur Built" experimental classification which has by far, the least restriction and it's clearly not possible to convert ("de-certify") a certified aircraft and end up with a Amateur Built experimental (The FAA has answered that question quite clearly).

What you can do is convert the airworthiness certificate to an experimental category that lets you flight test the deviation from the type certificate and in some cases it would allow you to demonstrate the result prior to obtaining a STC. But this comes with a price, typically only "required crew" can occupy the airplane in flight, flights are often restricted to a small defined area, and there's likely a time limit on the experimental certificate after which the plane would have to be returned to it's original state by removing the changes or by obtaining a STC "legalizing" the change.

 

[gismo]

I was thinking, after I posted this, that water/alcohol might be a better choice since it doesn't raise engine temps quite as much.

IIRC, water injection by itself doesn't significantly increase HP, it's typically used in conjunction with some form of supercharging (turbo or mechanically driven) where it allows an increase in the boost (MP) which actually provides the HP increase. In that case the water/alcohol is used a means of reducing detonation.

 

[Ted]

Like, for example, if you had an Aztec, took out the IO-540's and replaced them with IO-360's to increase range, and then used nitrous to help get your full 1800 lb payload into the air, then used the lower fuel burn rate of the 360 to get you further downrange.

They made an Aztec with IO-360s, it was called an Apache.

In practice, though, the fuel burn I get with my Aztec running economy cruise is about the same as the Apache, but faster. The takeoff and climb performance with IO-360s and a heavy load would be rotten.

I take your point, though. I would see the better reason to do something like add a turbo system that you otherwise couldn't due to certification requirements. And no, it's not a simple process or something you can realistically do. For certified aircraft to become experimental, you have to give a reason for it (typically a business purpose for R&D). It is valid for a limited amount of time, and you have to give a reason for it to be extended. When the experimentation is complete, it needs to be refitted to original configuration.

It would be easier to disassemble the aircraft entirely and then document reassembling it as an "amateur built" plane, which I've heard has been done but never seen it done.

 

[Henning]

You probably had better kits that were more scienced out and/or were just better at it. At my shop we put a few nitrous kits on the V12s and, while the engines responded well to it (especially coming with 11.5:1 compression out of the box), there weren't any readily available systems for them. That meant we had to put something together ourselves from components and, since we didn't do it all that frequently, it typically had problems. My concern is more that the problems may not be observable until the thing explodes.

A little 50 shot on a turbo car definitely does help get rid of the turbo lag, too.

I set all the nozzles to spray in above the valve like port injection, each cylinder gets a pair and tune each off a rail.

 

[Henning]

That leads me to another question. If you had a certified aircraft, could you "de-certify" it and have it re-classified as an Experimental aircraft??

Like, for example, if you had an Aztec, took out the IO-540's and replaced them with IO-360's to increase range, and then used nitrous to help get your full 1800 lb payload into the air, then used the lower fuel burn rate of the 360 to get you further downrange.

Or am I just smoking crack??

Couple of issues.

First, yes, you can decertify, however, it is not the same as amateur built experimental, it falls under Research and Development Experimental in order to be able to do the testing to develop the STC. You are very limited in how the aircraft can be used up until that point and you are monitored and supervised by the Feds to some extent.

As for putting IO 360s on the Aztec and doing spray take-offs, there's more involved such as the aircraft would be woefully underpowered in a OEI emergency when your bottle goes empty. It would not be my chosen idea of increasing economy since the IO 540 is basically equivalent in its BSFC as the IO 360, actually, it's a bit better and they have the same frontal drag profile. So really, you don't save much if anything if you just pull the IO-540s back and lean to the same HP the 360 will put out. You do though greatly limit your ability to run at higher power settings in head winds when it becomes beneficial.

 

[Ted]

I set all the nozzles to spray in above the valve like port injection, each cylinder gets a pair and tune each off a rail.

Yeah, NOS has been selling their systems like that, some of which even will bolt right in underneath the factory injectors.

I suppose it's what you're comfortable with. I'm much more comfortable with turbos.

Couple of issues.

First, yes, you can decertify, however, it is not the same as amateur built experimental, it falls under Research and Development Experimental in order to be able to do the testing to develop the STC. You are very limited in how the aircraft can be used up until that point and you are monitored and supervised by the Feds to some extent.

As for putting IO 360s on the Aztec and doing spray take-offs, there's more involved such as the aircraft would be woefully underpowered in a OEI emergency when your bottle goes empty. It would not be my chosen idea of increasing economy since the IO 540 is basically equivalent in its BSFC as the IO 360, actually, it's a bit better and they have the same frontal drag profile. So really, you don't save much if anything if you just pull the IO-540s back and lean to the same HP the 360 will put out. You do though greatly limit your ability to run at higher power settings in head winds when it becomes beneficial.

Yep...

 

[Henning]

Yeah, NOS has been selling their systems like that, some of which even will bolt right in underneath the factory injectors.

I suppose it's what you're comfortable with. I'm much more comfortable with turbos.



Yep...

No doubt, I would put on turbos before a bottle because of the gains it gets me in other flight regimes than T/O. I was just addressing the NOS type bottle issues on their own value.

 

[EdFred]

If we're not going to worry about certification - think going experimental - and you just want a boost on take-off or in an emergency, I'd go this route:
http://www.tecaeromex.com/ingles/peroxidoi.html

<day dream on>
~200 HP, fits in the palm of your hand, cool running and can be run for many minutes with fuel consumption in the range of a turboprop ... strap one on each wing mounted to reinforced spar and you've got yourself a VTOL :wink2:
<day dream off>

The ones in the hand are only 80-100lbs of thrust, not the 1100lb model.

 

[Capt.Crash'n'Burn]

As for putting IO 360s on the Aztec and doing spray take-offs, there's more involved such as the aircraft would be woefully underpowered in a OEI emergency when your bottle goes empty. It would not be my chosen idea of increasing economy since the IO 540 is basically equivalent in its BSFC as the IO 360, actually, it's a bit better and they have the same frontal drag profile. So really, you don't save much if anything if you just pull the IO-540s back and lean to the same HP the 360 will put out. You do though greatly limit your ability to run at higher power settings in head winds when it becomes beneficial.

I was looking at some modified high-compression IO-360's that make 230 hp @ 2700 rpm. Since you'd only be losing 20 hp, wouldn't it be beneficial to lose 100 lbs of engine weight??

Also, since a 4 cylinder has less internal friction than a 6, wouldn't there be lower fuel consumption per HP??

 

[Ted]

I was looking at some modified high-compression IO-360's that make 230 hp @ 2700 rpm. Since you'd only be losing 20 hp, wouldn't it be beneficial to lose 100 lbs of engine weight??

You'd really be losing 40 hp, which would be more significant. Weight does play into it, but at that point it seems to me like you'd really be better off looking at a hot-rodded Twin Comanche.

The Aztec has plenty of power so long as you're either not at gross or it's not summer. You'd also be having to spin the 360s faster to get your cruise power, making for more noise. When I first got the Aztec I tried to think about a couple of similar schemes, but I really don't see the advantage. Putting 300 hp engines in would be an advantage.

Also, since a 4 cylinder has less internal friction than a 6, wouldn't there be lower fuel consumption per HP??

There are a few other factors that play into it. End result is that if you look at economy of 4-cyl vs. comparable 6-cylinder engines, they're pretty darn close. To get 230 hp 4-cylinders vs. 250 hp 6-cylinders, you're talking about a very different engine and its SFCs would be different. At that point it's high compression, different head design, and a few other things. All of those impact your SFC. I don't know what the comparison would be at that point, but you'd basically be firewalling it and leaving it there for the duration of the flight.

 

[Henning]

I was looking at some modified high-compression IO-360's that make 230 hp @ 2700 rpm. Since you'd only be losing 20 hp, wouldn't it be beneficial to lose 100 lbs of engine weight??

Also, since a 4 cylinder has less internal friction than a 6, wouldn't there be lower fuel consumption per HP??

I made a 235hp IO 360 for my Midget Mustang, and that is most definitely an "Experimental" engine. Since you are turning more RPM to achieve the HP, that loss of efficiency overcomes the internal friction issues to make a wash at best.

 

[Doggtyred]

That leads me to another question. If you had a certified aircraft, could you "de-certify" it and have it re-classified as an Experimental aircraft??

Like, for example, if you had an Aztec, took out the IO-540's and replaced them with IO-360's to increase range, and then used nitrous to help get your full 1800 lb payload into the air, then used the lower fuel burn rate of the 360 to get you further downrange.

Or am I just smoking crack??

Yes.. but it would not be classed as Experimental Amateur Built. The available classes for you would be extremely limited in utility and would likely not be of value to you (restricted operations area, restricted travel, other limitations)

 

[Capt.Crash'n'Burn]

You'd really be losing 40 hp, which would be more significant.

In that case, you'd also be losing over 200 lbs.

The Aztec has plenty of power so long as you're either not at gross or it's not summer. You'd also be having to spin the 360s faster to get your cruise power, making for more noise. When I first got the Aztec I tried to think about a couple of similar schemes, but I really don't see the advantage. Putting 300 hp engines in would be an advantage.

Then perhaps high-compression pistons for the IO-540 is the solution??

There are a few other factors that play into it. End result is that if you look at economy of 4-cyl vs. comparable 6-cylinder engines, they're pretty darn close. To get 230 hp 4-cylinders vs. 250 hp 6-cylinders, you're talking about a very different engine and its SFCs would be different. At that point it's high compression, different head design, and a few other things. All of those impact your SFC. I don't know what the comparison would be at that point, but you'd basically be firewalling it and leaving it there for the duration of the flight.

I guess the 360 would be a little too stressed for the application, so how about this (now I am REALLY smoking low-grade crack). Lets say you took a IO-390, fitted it with a 4.625 crank, making it a 411, then added 10-1 pistons, roller cam, etc, you could easily make 250 HP@ 2700 rpm, and youre still 200 lbs lighter than with the 540's. The only comprimise that you'd be making, would be in TBO. (puts down the crack pipe).

 

[Capt.Crash'n'Burn]

I made a 235hp IO 360 for my Midget Mustang, and that is most definitely an "Experimental" engine. Since you are turning more RPM to achieve the HP, that loss of efficiency overcomes the internal friction issues to make a wash at best.

If I've got the specs on the 250 hp IO-540 correct, you'd only be turning 200 rpm more. It's not exactly in F-1 engine territory. :wink2:

 

[Henning]

If I've got the specs on the 250 hp IO-540 correct, you'd only be turning 200 rpm more. It's not exactly in F-1 engine territory. :wink2:

I was turning 2950 to make 235hp. If I wanted more HP out of a 360, my choice would be supercharging over Nitrous for sustainability of power.

 

[Ted]

I haven't picked up the engine specs for a while, but losing 200 lbs total I think might be a bit optimistic. You'd be going from a parallel valve 540 to an angle valve 360 (the angle valve heads weigh more). The weight savings would quickly be eaten up, though.

More than 2700 RPM is probably also a bit much for continuous operation reliably. The Continental IO-520-E engines spin to 2850 (or maybe 2875), but after 5 minutes you have to pull back, I pull back to 75% power on them. You'd probably end up needing to do similar.

As for taking a 390 and making it a stroker, well, at that point you're into all kinds of experimental, and I would really wonder why you didn't just go the easier, cheaper, and likely more reliable and fuel efficient route and go for the parallel valve 540s in the first place that came with the plane.

If you start out with 250 hp 540s, you could do some head work and/or high compression pistons to start. Of course, that gets into potential issues with detonation, torsional stresses on the prop, etc. The most reliable power boost is to put in an angle valve 540 or a 580, and that gets you 300-315 hp with OEM reliability. So, that'd be my first choice.

 

[Capt.Crash'n'Burn]

I was turning 2950 to make 235hp. If I wanted more HP out of a 360, my choice would be supercharging over Nitrous for sustainability of power.

I did get those #'s a bit off, it was 225 HP @ 2710, Which, according to a generic formula, is a volumetric efficiency ratio of 130%. Typical of many racing engines.

(The forumula, out of a Superflow Flowbench Manual) C.I.D. x V.E. x R.P.M. /5600= H.P. for gasoline, the constant for alcohol is 4750.

 

[Capt.Crash'n'Burn]

I haven't picked up the engine specs for a while, but losing 200 lbs total I think might be a bit optimistic. You'd be going from a parallel valve 540 to an angle valve 360 (the angle valve heads weigh more). The weight savings would quickly be eaten up, though.

I would have to see 'em side by side, but I can't imagine there being more than a few pounds difference.

More than 2700 RPM is probably also a bit much for continuous operation reliably. The Continental IO-520-E engines spin to 2850 (or maybe 2875), but after 5 minutes you have to pull back, I pull back to 75% power on them. You'd probably end up needing to do similar.

My hope was to have a 4 cylinder that only turned 100-200 more rpm's than the 540. What RPM does the 540 in the Aztec make peak HP at??

As for taking a 390 and making it a stroker, well, at that point you're into all kinds of experimental, and I would really wonder why you didn't just go the easier, cheaper, and likely more reliable and fuel efficient route and go for the parallel valve 540s in the first place that came with the plane.

My hope is that a big inch 4 cylinder will be able to beat the stock 540 in HP per Lb (should be easy), make 250 HP, and still be more fuel efficient.

If you start out with 250 hp 540s, you could do some head work and/or high compression pistons to start. Of course, that gets into potential issues with detonation, torsional stresses on the prop, etc. The most reliable power boost is to put in an angle valve 540 or a 580, and that gets you 300-315 hp with OEM reliability. So, that'd be my first choice.

Yeah, that would be the way to go for most circumstances, but I'm trying to find ways to push the range of the Aztec as far past 1,000 miles as you can possibly get.

 

[RotorAndWing]

The Lyc HIO-360-D1A used in the Schweizer 300C helicopter turns 3200RPM for normal operations and is derated to 190hp up to 4500'.

 

[Ted]

I would have to see 'em side by side, but I can't imagine there being more than a few pounds difference.

In a 6-cylinder engine, an angle valve weighs 50 lbs more than a parallel valve. Not much else is different, so figure you'd be about 35 lbs heavier. That takes 70 lbs out of your 200 lb savings, so you'd only be saving 130 lbs.

My hope was to have a 4 cylinder that only turned 100-200 more rpm's than the 540. What RPM does the 540 in the Aztec make peak HP at??

2575 RPM. Standard 4-cylinders are rated at 2700 RPM, helicopter ones have been higher (as R&W pointed out), but are then typically derated.

My hope is that a big inch 4 cylinder will be able to beat the stock 540 in HP per Lb (should be easy), make 250 HP, and still be more fuel efficient.

Think about what you're asking for. A stock parallel valve 4-cylinder makes 180 hp. A stock angle valve 4-cylinder makes 200 hp. Even the 390 I think is rated at 210 hp (someone else might know this better than me). You're looking at trying to add about 25% more power to an engine. That's not exactly a small feat. Compression will gain you some, but ultimately it comes down to getting more air in the cylinders, which will require some porting work and/or more RPMs. Let's not forget that the induction systems weren't designed to flow that much air, so you'll have to design a new induction system.

Possible? Yes. Reliable? Probably not. Fuel efficient? Definitely not moreso, at best it'd be equal. Your SFCs are not going to be much different, and that is ultimately what impacts your economy.

Yeah, that would be the way to go for most circumstances, but I'm trying to find ways to push the range of the Aztec as far past 1,000 miles as you can possibly get.

That's a much different question. Looking at raw range (no wind), the answer is more fuel. If you want to factor wind in, turbos that allow you to get up to higher altitude and catch some tailwinds will help, but only heading eastbound.

Basically, you aren't changing the efficiency of the airframe, so in order to get more range with the same fuel, you need to get better SFCs. The engine designs that exist for aircraft today will have some variation, but are in the same general range.

 

[Henning]

Yeah, that would be the way to go for most circumstances, but I'm trying to find ways to push the range of the Aztec as far past 1,000 miles as you can possibly get.

Slow down is the easiest solution, add fuel is another. You can also buy a Travel Air, I used to do 1100nm legs @ 135kts burning 6.1gph per side.

 

[Ted]

Slow down is the easiest solution, add fuel is another. You can also buy a Travel Air, I used to do 1100nm legs @ 135kts burning 6.1gph per side.

The Travel Air is very economical, as is the Twinkie. In my playing around with the Aztec, as you get much slower than 155 KTAS your fuel burn won't decrease much, and your efficiency will actually go down.

On my friend's Travel Air, we've gotten 155-160 at 7-7.5 gph per side.

 

[EdFred]

Slow down? What are you? Crazy?

 

[Ted]

Slow down? What are you? Crazy?

Slowing down can actually be faster.

Noodle on that one a bit.