I wanted it to look up to date so I modified it.

I wanted it to look up to date so I modified it. - Printable Version

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I wanted it to look up to date so I modified it. - Orv Neisingh - 08-06-2026

The photo below was taken at one of our Western States Fly-ins back in the early 1990's at the Orland County airport in northern California. Sheila and I are flying our Exec 152 past friends checking out a Scorpion II while Dan Vandusen was doing aerial photo shoots from his Exec 152. About this time Rotorway came out with their latest model the Exec 90. The 90 had landing gear that was around 6" taller than those on the 152, A taller main rotor shaft by 6" and the doghouse did not have the air intake hole in the front that the 152s all had.

I wanted to modify my doghouse to make it look like the new Exec 90, who needs a hole in the front of the doghouse anyway? With a couple of late evenings worth of work I covered the hole with fiberglass and painted it to match the rest of the doghouse and I was really proud of my handiwork. I hovered the helicopter and monitored the temps and all appeared normal after the modification.

Some friends invited us to join them for lunch in Lower Lake on the shore of Clear Lake in northern California and I was excited to show off my dog house modification to them. We set a time for Sheila and I to meet them and called just prior to lifting off. It was about a 60 mile flight which we could easily accomplish in about an hour. We left our home around 11am and began transitioning our route from the Sacramento valley over the coastal range mountains. Our route had us climb several thousand feet and as we climbed over the highest mountain on our route Sheila told be to land because she was getting burned on her thigh.

The Execs did not have an enclosed collective slot for the middle collective, the slot was open to the tub and engine compartment. My modification of closing off the hole in the front of the doghouse had dramatically changed the air flow in the engine compartment and now hot air off the exhaust pipes was entering the cabin through the center slot, right below the passengers thigh. As we climbed over the mountain at full power and slower airspeed, the intense exhaust heat was literally blistering my wife"s thigh. She told me "Land now or I will land it!".

Near the top of the mountain there was a small grass covered meadow so I entered an auto, flared and landed on the flat grassy "meadow". As I lowered the collective the surface gave way and the skids began to sink as grey mud oozed up over both skids. This was not a meadow but a grass covered mud bog with about an inch of dry cracked soil covering the mud. As I lifted the collective to keep from sinking the pilot side skid broke free of the
mud's suction but the passenger side skid held firm and as I added collective input the helicopter tilted dangerously to the passenger side...what to do??

Sheila was hurting and our helicopter was trapped in a mud bog on top of a isolated mountain at a serious right tilt. I did not dare to lower the collective because we would just sink more into the bog. I then recalled a previous flight instructor telling me about getting a skid stuck on the ice of a frozen lake. He had told me that he was able to break free by using the anti-torque pedals to wiggle the helicopter back and forth with upward collective and it broke free of the ice so that is what I did. As I wiggled the helicopter back and forth with just enough collective to keep from sinking the right skid came up out of the mud and I was then able to skid the helicopter lightly across the dry surface to the shore line where there were some rocks so I assumed it was solid there, it was. At that altitude above sea level the little Exec did not have the power to totally break the ground and hover so skidding it was all I could do.

I shut the helicopter down once we were resting on solid ground and sheila jumped out and checked her burns, sure enough she had several large burn blisters on the side of her left thigh. I realized that my dog house hole covering modification had drastically changed the airflow through the engine bay and was the reason for the burns to my wife's leg. I always fly with my Leatherman multi-tool and I used it to cut out the fiberglass cover over the hole in the doghouse, it wasn't pretty but it would do. Our present altitude on top of the mountain was well above our near sea level hover performance and I had to get airborne to depart this desolate bog.

With the low-powered Execs it was not uncommon to run the main rotor RPM up to the red line then increase collective to jump the helicopter off the ground so that is what I did. As we jumped off the surface I made a left turn letting the torque turn the nose of the helicopter as a right turn would require anti-torque and rob the engine power to the main rotor and I needed every bit of that power to accelerate through ETL. Once through ETL we continued our flight and as we approached the Lower Lake gang anxiously waiting for us we could see that they were relieved that we had made it although we were over due.

When we landed we were told that they knew there was a story to tell by the long clumps of grass and mud still hanging from the helicopter skids. We had a great visit, a good lunch, and shared lessons learned. One of the guys there to meet us was Nathan Fronsman with his wife Elaine. The other was Len Chriysler. I have an interesting story of one of Nathan's modifications that did not fare well either, for another time.

[Image: Screenshot-2026-08-06-at-06-39-30-Rotorw...e-Page.png]

RE: I wanted it to look up to date so I modified it. - Tim Morris - 08-06-2026

Orv, has anyone ever done a study using string and video to show how the air flows through our ships in a hover and forward flight? Seems like we could do a lot of useful modifications that would improve cooling. Experimenting can lead to the issues you experienced. Graeme has done some interesting stuff in this area, but it seems like we should be able to get more cool air to the engine and radiator without extensive modifications.

I still can only get about 10 minutes of hover training done for my bride before we reach redline. I have purchased an electric water pump, but I am not convinced this will fix the problem and this is a big modification to undertake only to find out it didn't fix the issue. When I hover without any cowl, it seems to stay cooler. This tells me I have an airflow problem, not a water circulation problem.

I think before I do the electric water pump, I am going to cut holes in the upper rear cowl to allow more cool air direct to the radiator. Would be nice to have a study show the airflow rather than experimenting. But the helicopter has a big EXPERIMENTAL label on it, so....

RE: I wanted it to look up to date so I modified it. - Lyle Swallows - 08-06-2026

there was a good thread on ROG showing inflight string flow tests with the belly of the helicopter stemmed from an owner or two having over heating issues while in forward flight... but they could hover without overheating. every build seems to be a "your mileage may vary"

i personally am exploring Graemes ducted radiator design with electric fans. but you're right this is an area that needs extensive work to make complete. upgrading electrics mainly...

i'm only doing so since my build is a complete re-fit.

RE: I wanted it to look up to date so I modified it. - Orv Neisingh - 08-06-2026

(7 hours ago)Tim Morris Wrote: Orv, has anyone ever done a study using string and video to show how the air flows through our ships in a hover and forward flight? Seems like we could do a lot of useful modifications that would improve cooling. Experimenting can lead to the issues you experienced. Graeme has done some interesting stuff in this area, but it seems like we should be able to get more cool air to the engine and radiator without extensive modifications.

I still can only get about 10 minutes of hover training done for my bride before we reach redline. I have purchased an electric water pump, but I am not convinced this will fix the problem and this is a big modification to undertake only to find out it didn't fix the issue. When I hover without any cowl, it seems to stay cooler. This tells me I have an airflow problem, not a water circulation problem.

I think before I do the electric water pump, I am going to cut holes in the upper rear cowl to allow more cool air direct to the radiator. Would be nice to have a study show the airflow rather than experimenting. But the helicopter has a big EXPERIMENTAL label on it, so....

Tim, when we do hover training we most often leave the rear upper and lower cowling off for better cool air flow. Rotorway experimented with ducts to bring fresh air into the radiator but the ducts and fiberglass manifold were in the way of our pre-flights. They also had the builder fabricated aluminum shields extending from the radiator to the rear tub area with slots around the exhaust. This too proved to not make a difference and they finally eliminated this heat shields from the Talon kits. When students had them on their ships I suggested that they remove them and most did that.

RE: I wanted it to look up to date so I modified it. - Geno Mancini - 08-06-2026

Graeme Smith claims to have solved the over heating problem.
It seems to be a very extensive mod, though.
Basicly, he removes the mechanical fan and directs fresh air to the top of the radiator.
Has electric fans on the bottom of the radiator, sucking the hot air out.

Scroll down his FaceBook page to see it.
https://www.facebook.com/groups/1523964747814153/user/100058403720564

RE: I wanted it to look up to date so I modified it. - Tim Morris - 08-06-2026

(3 hours ago)Geno Mancini Wrote: Graeme Smith claims to have solved the over heating problem.
It seems to be a very extensive mod, though.
Basicly, he removes the mechanical fan and directs fresh air to the top of the radiator.
Has electric fans on the bottom of the radiator, sucking the hot air out.

Scroll down his FaceBook page to see it.
https://www.facebook.com/groups/1523964747814153/user/100058403720564

Geno thanks, I have seen that mod and I have been in conversation with him. Very extensive mod. I may have to go there in the end, but I would like to try easier stuff first.