# Traveling with a twin engine 2 stroke airplane?

### Help Support HomeBuiltAirplanes.com:

#### blane.c

##### Well-Known Member
HBA Supporter
Extra engines Lazair

#### Armilite

##### Well-Known Member
As you know if you have a total of 50hp with two engines it is unlikely to maintain altitude on a single engine (with any appreciable weight) because of losses due to drag will make the effective power available closer to 37% than 50% so on single engine you will have effectively more like 18hp than 25hp. Also you likely don't cruise @ full power so being on one engine will be a judgement call, if in order to maintain some kind of glide path better than complete engine loss you decide to reduce power on the one remaining due to engine temps going up regards power setting and airspeed.

My crazy thinking is three engines are better. Usually with three engines one will be in the center and will not adversely affect yaw and therefor not be included to any appreciable degree in drag losses due to the failure of either engine mounted on the side. So worst case if you lose a side mounted engine on an aircraft with (3) 17hp engines (51hp total) then you would have effective power of 37% of the two side mounted engines plus the full power of the center engine so 37% of 34hp = 12.5hp effective + 17hp center engine equals 29.5hp effective which is over 10hp better than a twin with a engine loss and much more room to reduce some power a bit to maintain temps.
==============================

With a Triple, your Cost & Weight goes up. Even most Commerical made Small Twins aren't being produced today. I haven't seen a Triple made since WWII.

The Lazair is a unique Plane account it was really more of a Motor Glider than an Ultralight and flew on (1) 9.5hp Engine, originally used (2) 5.5hp = 11hp.

Most Twins ever made don't share that Power to Weight Ratio!

A 2 Stroke or 4 Stroke can be built to be more Durable. You Can't Fix Stupid people who run out of Gas, forget to put Oil in the Engine/Gas, use cheap Low Octane Gas, don't change the Plugs, Fuel Filter, etc.

Just like when upgrading these Honda/Clones Singles, 99% only do the $400 worth of upgrade Mods, but yet the weakest Point on a 4 Stroke is the Valve Train. I would spend the extra$180-$200 and use the HD Billet Needle Bearing Rocker Arms. I would also use these Engine Coatings. This adds to the total Engine Cost, but you can do them yourself fairly cheap. #### Speedboat100 ##### Well-Known Member I am curious what the responses would be if a new cheaper design came out utilizing small twin 2 strokes....yea or nay? Cri Cri is such. It can also be fitted with jet engines. #### Toobuilder ##### Well-Known Member HBA Supporter Log Member I am curious what the responses would be if a new cheaper design came out utilizing small twin 2 strokes....yea or nay? A response would require some significant requirements definition, but even for talking points : "Cheaper" than what? What is the cost theshold you are trying to met? What is the mission of the aircraft -speed, range, payload, seating capacity, etc? What FOS are you trying to meet with a twin? Is the proposed configuration any safer or more reliable than the existing products? #### blane.c ##### Well-Known Member HBA Supporter ============================== With a Triple, your Cost & Weight goes up. Even most Commerical made Small Twins aren't being produced today. I haven't seen a Triple made since WWII. The Lazair is a unique Plane account it was really more of a Motor Glider than an Ultralight and flew on (1) 9.5hp Engine, originally used (2) 5.5hp = 11hp. Most Twins ever made don't share that Power to Weight Ratio! A 2 Stroke or 4 Stroke can be built to be more Durable. You Can't Fix Stupid people who run out of Gas, forget to put Oil in the Engine/Gas, use cheap Low Octane Gas, don't change the Plugs, Fuel Filter, etc. Just like when upgrading these Honda/Clones Singles, 99% only do the$400 worth of upgrade Mods, but yet the weakest Point on a 4 Stroke is the Valve Train. I would spend the extra $180-$200 and use the HD Billet Needle Bearing Rocker Arms. I would also use these Engine Coatings. This adds to the total Engine Cost, but you can do them yourself fairly cheap.
If you want the most efficient airplane and don't care about anything else then single engine is the way to go.

Twins are not produced because "they are inefficient, so is a triple", but it is inefficiency of a bygone era's opinion. There is a different type of efficiency gained with a three engine arrangement and that is the ability to make it to a runway if you have a loss of engine power or much better odds of it. I often see in the evening news a ga airplane accident and most of them are single engine. It isn't just because there are more single engine aircraft it is because a single engine aircraft has much less chance of making it to a runway than a multi-engine when there are engine problems.

I argue that a triple isn't a lot more expensive than a twin because the engines can be smaller than the twins engines and their smaller size offsets part of the expense. I also argue that a engine out in a triple is much easier to deal with than an engine out in a twin, because (unless you go to extreme sizes of engine on the twin) you will have more remaining power available with an engine loss with the triple and also less adverse yaw to control.

HBA Supporter

#### Toobuilder

HBA Supporter
Log Member
If thats true, then the Rotax costs $135 bucks per HP. Multiply that by 180 and you are right in Lycoming 0-360 country. #### Wanttaja ##### Well-Known Member Well, most engine setups end up being upwards$7-10k so was just thinking about cost vs reliability.
Don't think "reliability" is the term you're looking for. Adding a second engine only doubles the chance of an engine failure.

You're undoubtedly looking at the ability to continue the flight to a safe destination, vs. having to perform an immediate power-off landing. One of the OWTs about flying is that you're actually MORE likely to get killed after engine failure on a twin-engine aircraft. The way the story goes, pilots fly "power-off" landings all the time, but the gymnastics needed to keep a twin going with a fan out is something practiced only BFRs. A VMC roll at low altitude is very likely to kill you.

Again, though, just a story...haven't seen any sort of statistics on it.

Light twin aircraft rarely have a surfeit of power. Do so research on the Champion Lancer, a twin-engine version of the Aeronca Champ. Thing couldn't get out of its way with one engine out.

To maximize safety, too, you're going to want to have featherable propellers on the engines...kind of rare, for two-stroke engines. That was the downfall of the Lancer, two O-200s with fixed props. If your plane can't climb on a single engine, you're just stretching the glide, which may or may not really be an advantage. Though maybe two-stroke engines don't windmill....

Two-stroke engine issues are a factor in homebuilt aircraft accidents about twice as often as certified aircraft engines. If safety is your goal, you'd be better off with a single, more reliable powerplant instead of two two-stroke engines.

Ron Wanttaja

#### Hephaestus

##### Well-Known Member
With a Triple, your Cost & Weight goes up. Even most Commerical made Small Twins aren't being produced today. I haven't seen a Triple made since WWII.
Britten-Norman would dispute the lack of triples.

Caught a ride on one down in ? St Kitts? years ago.

#### n3puppy

##### Well-Known Member
Britten-Norman would dispute the lack of triples.
Caught a ride on one down in ? St Kitts? years ago.
So would de Havilland (DHA-3 Drover)
There are more in this thread
THREE ENGINE AIRCRAFT

#### Armilite

##### Well-Known Member
If you want the most efficient airplane and don't care about anything else then single engine is the way to go.

Twins are not produced because "they are inefficient, so is a triple", but it is inefficiency of a bygone era's opinion. There is a different type of efficiency gained with a three engine arrangement and that is the ability to make it to a runway if you have a loss of engine power or much better odds of it. I often see in the evening news a ga airplane accident and most of them are single engine. It isn't just because there are more single engine aircraft it is because a single engine aircraft has much less chance of making it to a runway than a multi-engine when there are engine problems.

I argue that a triple isn't a lot more expensive than a twin because the engines can be smaller than the twins engines and their smaller size offsets part of the expense. I also argue that a engine out in a triple is much easier to deal with than an engine out in a twin, because (unless you go to extreme sizes of engine on the twin) you will have more remaining power available with an engine loss with the triple and also less adverse yaw to control.
===================

First, you have to look at 40+ Years of Prior Accident Data! It's about 50/50 between Ultralights/Kitplanes and Small Commerical made Airplanes. The Top three leading causes for many years are:

1. Running out of Gas! (Human Error)
2. Flying in Bad Weather! (Human Error)
3. Flying with a known Mechanical problem. (Human Error)

There Top 10 today.

10) Thunderstorms Or Windshear (Human Error)
Weather is obviously one of the most hazardous parts of flying. This photo below is a Cessna 210 that flew into a level 6 thunderstorm. The pilot at the controls was Scott Crossfield, an accomplished Naval test pilot, and the first pilot to fly twice the speed of sound. Before he departed, he received a weather briefing, however he didn't get weather updates during his flight. The airplane broke apart in-flight, with wreckage found at three different locations.

9) Midair Collisions (Human Error)
Most midairs happen near airports, and in this accident, a Cessna 172 entered the traffic pattern and collided with a helicopter. Unfortunately, the 172 didn't make radio calls prior to entering the pattern, and the helicopter was unaware of them. The helicopter was able to land safely, but the 172 entered a spin, impacting the ground.

8) Systems Failure
This Cessna 335's attitude indicator failed in poor weather. The pilot became spatially disoriented and crashed.

7) Fuel Exhaustion Or Contamination (Human Error)
This Cessna 172 ran out of fuel in flight. The aircraft had just completed an STC (supplemental type certificate) to increase the engine's horsepower. However, new fuel burn rates weren't placed in the flight manual, and the pilot didn't plan for the increased fuel burn rate.

6) Flight In IMC (Human Error)
This King Air 200 was on a localizer approach, but the pilots were using a GPS to navigate to the IAF. The pilots inadvertently swapped the initial approach fix with the missed approach point on the GPS, using manually entered fixes. With no glideslope, and incorrect DME data, the plane flew approximately 5 miles past the missed approach point at the MDA altitude. As the pilots executed a missed approach, they impacted the top of a mountain.

5) Unknown/Undetermined
Sometimes the NTSB and FAA don't have enough information to determine the cause of an accident. In this crash, the NTSB and FAA believe the aircraft flew into a severe downdraft in mountainous terrain, based on radar data. Carb Ice is also hard to detect.

4) Low Altitude Operations (Human Error)
This P-3 air tanker was on a fire bombing run. The flight had an FAA examiner on board performing a checkride. As the P-3 descended over a hill, the left wingtip hit the ground, and the aircraft impacted terrain.

3) Powerplant Failure
In this crash, the aircraft had a right engine cylinder failure. The pilot feathered the prop but didn't have enough single-engine performance to maintain altitude. The pilot elected to ditch the aircraft in the water. Fortunately, the pilot and all the passengers survived.

2) Controlled Flight Into Terrain (Human Error)
This King Air 200 was on a medivac flight. The pilot was cleared for a visual approach into Bozeman, MT at night. Unfortunately, the pilot identified the wrong airport, overflew Bozeman, and impacted terrain.

1) Loss Of Control In Flight (Human Error)
In this accident, the pilot lost their right engine immediately after takeoff. The pilot lost directional control, rolled inverted, and impacted the runway.

You say "efficient" but I think you mean more Durabil or Safe. Let's say you have a Cessna 310, (4) Passengers and Full Fuel and then takeoff, get maybe 50 miles, and have an Engine Failure. Now is it going to make it back to the Airport?

General characteristics
• Crew: one
• Capacity: four passengers
• Length: 27 ft 0 in (8.23 m)
• Wingspan: 35 ft 0 in (10.67 m)
• Height: 10 ft 6 in (3.20 m)
• Wing area: 175 sq ft (16.3 m2) [75]
• Empty weight: 2,850 lb (1,293 kg)
• Gross weight: 4,600 lb (2,087 kg)
• Fuel capacity: 100 US gal (83 imp gal; 380 L)[75]
• Powerplant: 2 × Continental O-470-B horizontally opposed piston engines, 240 hp (180 kW) each. 480 hp total.
Off a different website:
5 MOST COMMON CAUSES OF AVIATION ACCIDENTS

Aviation accidents often take years to fully investigate, and so the exact cause of a plane crash may not be discovered for some time. However, there are several causes that have been found to be contributing factors in most aviation accidents:

1. Pilot error. The most common cause of aviation accidents is pilot error, which accounts for approximately half of all plane crashes. Flying a plane is among the most complex and difficult jobs available, despite modern innovations that automate many features of air travel. A pilot must monitor dozens of readouts and gauges throughout the flight, many of which seem downright mystic to non-pilots. Any miscalculation or misreading can result in a deadly crash. However, pilots should not be blamed for every accident.

2. Mechanical defects. Planes are massive feats of engineering and are made up of hundreds of separate systems. A defect or failure in any one of these systems can lead to a dangerous situation. These can include manufacturing defects, inadequate repairs or equipment replacements, and old or worn out parts.

3. Weather problems. Just as driving becomes more dangerous in bad weather, so does flying. Heavy rainstorms, fog, and snow can make it more difficult for airplanes to maneuver and can lead to deadly accidents. Visibility issues, high winds and skidding during takeoff and landing are the most dangerous weather-related threats to aircraft.

4. Air traffic controller error. Pilots rely on information and support from air traffic controllers while they are in the air. Air traffic controllers must coordinate with many different planes at once, and often must take factors such as weather and fuel into consideration when scheduling takeoffs and landings. Any error made by an air traffic controller has the potential to result in an aviation accident, possibly involving more than one aircraft.

5. Other causes. There are many other factors that can contribute to a plane crash, including sabotage and poor runway maintenance. One of the most surprisingly common factors in aviation accidents is birds. If a large bird collides with a windscreen or an engine, it can cause damage that may contribute to a plane crash.
Notice, Engine Failure isn't really a problem, it's Pilot/Human Error for not Maintaining their Engine. I would say 99% of all Engine Failures are Human related.

#### EzyBuildWing

##### Well-Known Member
Aircam with twin Rotax 4-stroke pushers can can easily climb-out on one engine at max gross.
Plenty of Youtube vids demonstrating Aircam climb-out on one.
How about a Moyes Dragonfly powered with THREE pusher Polini-Thor motors..... 36HP each, 18 kg, and 105kg thrust with a 1.5m dia prop?.......would give the pilot a substantially better chance of making a power-on decent/landing if one(or two) engines quit.
Hey, if 3 engines all quit together, then go for the ballistic-chute option!

HBA Supporter
BS

#### Wanttaja

##### Well-Known Member
Notice, Engine Failure isn't really a problem, it's Pilot/Human Error for not Maintaining their Engine. I would say 99% of all Engine Failures are Human related.
Since engines and aircraft are created by humans, any failure is thus human-related. Humans designed them, humans built components, humans assemble them, and humans operate them. On that basis, 100% of all accidents, not just engine failures, are "human related." Guess I should just delete my databases and relax.

I think it was Robert Heinlein who said, "When you get down to it, all deaths can be attributed to heart failure."

Ron Wanttaja

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Just need two hearts.

#### Wanttaja

##### Well-Known Member
Just need two hearts.
Obviously, only Time Lords should fly.

Ron Wanttaja

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Oh, instead of traveling with twins it's traveling in time.
I had to look that one up on wiki:
Time Lords and human beings look alike,[38][39] however they differ in many respects. Physiological differences from humans include two hearts which normally beat at 170 beats per minute,[40] three brain stems [S10E06 Extremis], an internal body temperature of 15 degrees Celsius (59 degrees Fahrenheit)[citation needed] and a "respiratory bypass system" that allows them to survive strangulation

HBA Supporter

#### Toobuilder

##### Well-Known Member
HBA Supporter
Log Member
Based on the graphic in post #34, Im never going to set my azz in a Glassair III... Way too dangerous!

#### TFF

##### Well-Known Member
Is that 104% chance of engine failure?