Hot Shot Performance

[ksandrew]

Hi All,

Although I have been flying the Hotshot for four years I still do not consider that I know it as well as I should.

Planning the Alaska trip that will be at gross weight on every take off, and flying there via Mexico with the July heat, I need every bit of information that is out there.

The POH with its ammendments for the Hotshot are not that informative. "Meets or exceeds original aircraft" does not tell me a lot.

On many hot South Georgia days I am excited just to get 300 fpm.

For the Hotshot owners out there, what do you do at sea level on a hot day to get off the ground?
I have heard of the 30" for 3 min, but during the take off roll is not a time to be adjusting things for me. I have a hard enough time keeping it on the runway.

open to any ideas or tips. I am a B so have the longer wings and more drag.

Life is a barrel of fun.

Ken Andrew.
N377SB 112B Hotshot sn.526
Albany,Ga.USA

 

[rotarur]

Re: Hot Shot Performance

Ok, once again, this works for me all the time at sea level. If I am heavy loaded and don't have too much runway, I do a "soft field" takeoff to get up in the air ASAP. The moment the mains are off the ground I lower the nose gently and accelerate in ground effect. I build enough speed to be able to climb at 6-700 ft/min up to pattern altitude in no time during a hot day. Also, don't be afraid to raise the nose to climb slowly but steeply if you need to - this method saved my bacon at least in one ocassion, although I needed to clear some leafs and small branches from my landing gear after I landed - just watch your airspeed and be coordinated. It does not look very comfortable for the passengers and it's quite nerve wrecking for you as a pilot, but hey, these are maximum performance takeoffs and the plane is capable of doing it if you're doing it right. Also, longer wings means more air foil and more lift as well, no?

 

[ksandrew]

Re: Hot Shot Performance

Radu,

I have not seen 700 fpm since the winter morning I was doing touch and go's, alone, and ran out of fuel on downwind.

Life is a barrel of fun.

Ken Andrew.
N377SB 112B Hotshot sn.526
Albany,Ga.USA.

 

[sfaret]

Re: Hot Shot Performance

Not sure of the problem yet Ken, I do see 1100 FPM in the right conditions. 7500-700 is more the norm.
Not sure what the 112B wing does on climb out.

 

[atjudge]

Re: Hot Shot Performance

Ken: My number's are almost Identical as Sven's. I've got your wing and 10 more HP than he does. I don't see 300 fpm unless it's really hot and I've got 3 peeps and full gas. The TC manual calls for 38" on climb instead of 40-42 for take off, so I think I'm using the same HP in climb as the HS's do. Time for some trouble shooting...

 

[KellyB]

Re: Hot Shot Performance

I fly my HS at high DA's a lot in the summer. I find that getting off the ground and accelerating to 90 knots gives me a much better rate of climb. The book numbers for climb out are fine at sea level when it's not too hot, but at 4000 ft on a hot day, they don't work. I see 800 ft/min regularly once I'm cleaned up and flying at 90. if I slow it up, the rate of climb goes down. That's with 26" of MAP. On a high DA day I think you are actually on the back side of the power curve at 80 knots. I flew out of St George, UT a month ago at max gross and did fine, just couldn't climb worth a darn till the speed built up.

 

[ksandrew]

Re: Hot Shot Performance

Last night I did a high performance take off with the hotshot.

Sat at the end of the runway and had it all thought out.

The plan was to hit the timer on take off roll and go for the 30" of MP for 3 min. and hold the airspeed at 80 knots.

On the roll I was winding in the wastgate looking for 30"

The climb was like I have never seen it before, the nose just pointing up, almost like Concorde.

I was being very careful not to exceed the 30" but I could not wind it in fast enough, had to take my hand off to raise the gear, almost like I had it all the way in.

I am going to try it again tomorrow, It was unbelievable.
Those that say turbo normalizing at sea level has no advantages are wrong.

Life is a barrel of fun.

 

[sfaret]

Re: Hot Shot Performance

Full fuel, 3000 foot 95* hot summer day. Gross+, high trees at the end.
33" mp till clear of trees then 28.5"@2700 to 16000 in 25 minutes.

I limit my climb speed as oil temp dictates. Adding a crack of cowl flaps does 8* cooler. Adding full cowl flaps does nothing more. CHTs are always ~380 or less in this climb config. usually 320-340*.

Nice and cool, headed home with high alt tail winds.

I normally dont fly like this but that day I did. usually 8-12000. more casual climb.

 

[ksandrew]

Re: Hot Shot Performance

Sven,

You have some typo errors in you post, you said Gross+. I am sure that was just a typo.

I know that you would never exceed gross weight.

33" MP, How many hours did you get on that engine????

I am not expert, do you think 33" is ok for just a while????

I do tend to over "BABY" my engine.

I am not sure that I could wind in the waste gate that fast. Did you have it wound in before the takeoff roll?????????

What to you was an acceptable oil temperature??????? During climb.

I am still learning and would like to fly with a more experience Hotshot owner.

Life is a barrel of fun.

 

[sfaret]

Re: Hot Shot Performance

Sven,

You have some typo errors in you post, you said Gross+. I am sure that was just a typo.

I know that you would never exceed gross weight.

33" MP, How many hours did you get on that engine????

I am not expert, do you think 33" is OK for just a while????

I do tend to over "BABY" my engine.

I am not sure that I could wind in the waste gate that fast. Did you have it wound in before the takeoff roll?????????

What to you was an acceptable oil temperature??????? During climb.

I am still learning and would like to fly with a more experience Hotshot owner.

Life is a barrel of fun.

HA! Obviously learn by me and you'll PAY!
11 cylinders since new on the old motor.
However 7 of them were from a poor overhaul back in 1987 all dumped by 1990. Since, 2 cracked oil rings and 2 sticking exhaust valves.

That 33" stuff was only 2 short 1 minute episodes.
got 1800hrs but that # is tainted due to all the Cly stuff.

I cant explain the cracked oil rings.
Oil Temp norn for me is climb~230 hot= ~242. norm~210

I rolled it in on the roll. ya get the feel for it.

I you did fly with me and remarked on the throttle changes, Gotta do when gotta do. Fun costs. Down low you need it off and on.

More post on the current motor later.

 

[FS]

Re: Hot Shot Performance

33" MP, How many hours did you get on that engine????

The highest recorded surface barometric pressure was 32.01". So just think about how that relates to what your engine should be capable of handling.

 

[Dave]

Re: Hot Shot Performance

The highest recorded surface barometric pressure was 32.01". So just think about how that relates to what your engine should be capable of handling.

Frank,

If I'm understanding you correctly it seems as if you are saying that our engines should be able to handle at least 32.01" and then some, since it is an atmospheric possibility.

I think the WWII aircraft like the P-51 actually had manifold pressures in the 50-60" range for take off (not sure of this) Obviously the Merlin is a pretty beafy engine and was designed for this.

Would the case pressure be the factor, or the difference between case pressure and ambient pressure be the issue?

 

[Commander91gm]

Re: Hot Shot Performance

The 112TCA take off MP limit is 42" at sea level. Cruise @75% is around 34" and 2,400 rpm. I do this all the time.

Would not be concerned about pushing the hot shot to 33". Doubt it would have much effect on TBO

 

[sfaret]

Re: Hot Shot Performance

Whole different animal guys. 28.5 redline with the IO360 cylinders.
Higher compression ratios and etc.

O360's get power from lower compressions and higher pressure. More gas and high temps, no intercooler.

IO360 is "normalized" sea level. 28.5 max. 33 is puishing it hard.

 

[nruzic]

Re: Hot Shot Performance

Frank,


I think the WWII aircraft like the P-51 actually had manifold pressures in the 50-60" range for take off (not sure of this) Obviously the Merlin is a pretty beafy engine and was designed for this.

Would the case pressure be the factor, or the difference between case pressure and ambient pressure be the issue?

The P-51D Packard built Rolls Royce Merlin 61 engine had a boost pressure of 70ish inches in war emergency throttle (short time more than full throttle rating). Remember they had 2 speed engine driven superchargers, 100/150 octane fuel and intercooling all allowing a reasonable detonation margin (the engine compression ratio was little more than 6 to avoid detonation).

Sven is correct (as usual) turbo normalizing and turbocharging are different. In general the boosted engines will be designed for the effects of the extra manifold pressure and the coupled need to maintain detonation margins.
If a regular engine is normalized after market we need to be sure detonation margins are addressed via intercooling or modified to lower compression pistons to maintain the detonation margins.

 

[FS]

Re: Hot Shot Performance

If I'm understanding you correctly it seems as if you are saying that our engines should be able to handle at least 32.01" and then some, since it is an atmospheric possibility.

Yes, unless you see a placard which says something like "do not operate above 30 inches atmospheric pressure". One of the more engineering oriented folks might post a design maximum manifold pressure for a normally-aspirated engine.

Just think about the product liability issues if engines blew apart the day the surface atmospheric pressure went above 30" or 31".

 

[Dave]

Re: Hot Shot Performance

Thanks for the clarification Sven

Dave