Seagull DH-98 Mosquito engine choice

[Martin Harris - Moderator]

Jon, while you are perfectly correct in that an engine failure in a twin is a handleable situation, this assumes a good skill level plus the confidence borne of familiarity with the model and/or situation. I have lost count of the number of twins that I've seen lost at airshows where the assumedly experienced pilots have spun in after an engine failure. These include both normal public and LMA organised events.

The model is an important factor - my Slim Twin being at one end of the spectrum and something like a Mossie at the other. I've lost an engine on the Slim Twin at takeoff and continued to fly until the other engine's tank was virtually empty but based on personal observation, in average hands (and I include mine) the best thing to do with a high wing loaded, low asymmetric powered twin is to get it safely on the ground with the minimum risk of terminal damage. In my opinion, for most mere mortals, the safer option is to close the throttle and treat it as a deadstick.

This is different to arranging to simulate an engine failure where the failure will not require identification of the dead engine and logical thought under pressure - turning into the dead engine while climbing out (quite a common scenario) may well be enough to provoke a spin - treating that situation as a deadstick might result in some minor damage in an adjacent field.

On the other hand, if you can arrange differential engine control, practicing engine failure at a good height and position can only be a good thing - even better if you can randomise the failure. If you've done so regularly and have gained confidence then you can consider single engined operation of the model in the event of an actual engine or motor failure but don't underestimate the stress factor of a real situation which can hamper logical and cool thinking.

It could be argued that the more reliable the power sources have become, the more dangerous a failure becomes. If you were to expect a failure at any time, you would be less likely to be taken by surprise when one happened - and of course this is the mindset you should adopt with any aircraft - but human nature is a dangerous enemy.

Final thought, in the full size world there's a saying:

"The purpose of the second engine is to enable you to get to the scene of the crash..."

P.S. Just read your most recent post which overlapped - I do agree with your described methodology which should give a good chance of success but I still feel it preferable to advise people to adopt the deadstick method unless they have gained considerable skill and experience of handling their aircraft on a single engine.

P.P.S. As far as I'm concerned, I'd call a deadstick and disregard the semantics of whether you have partial power as the last thing you want is any confusion in the circuit at what is a stressful time for most pilots.

Edited By Martin Harris on 17/10/2017 11:10:20

[Piers Bowlan]

I have to agree absolutely about the benefit of practicing engine out flying on a regular basis particularly on a model you are familiar with and that follows full sized practice. However if the model is new it is probably more likely to suffer a failure and of course practicing engine failures is in itself not without risk. Also, how realistic is it? Flying up the strip into wind at a good height and deliberately closing a throttle is one thing. Turning base onto final with the gear down and the engines at low power is something quite different. Low height, low speed, coming towards you and one engine cuts as you open the throttles to reduce the rate of decent; the aircraft can auto-rotate before you can say 'flat spin'. Near the ground that is terminal. Best make sure the engines are set up right as Jon suggests and get in plenty of practice.

[Jon H]

The reason i am not a fan of the cut and glide idea is that you are then adding another unknown risk by trying to put it down in the field and risk damage that way. Given that most twins i have owned glide like bricks I would rather maintain the speed and power with the remaining engine and fly home.

The key is maintaining control in the first few seconds, and i appreciate completely that some models are less helpful than others when it comes to loosing an engine.

Perhaps i should clarify a few points though.

Engine sag on takeoff - abort immediately! do not try and carry a sick engine into the air.

Engine failure on climb out - Get the bin bag. Depending on the model you might fly it out, but you also might spin it. Personally i would try and fly it out, but if it didnt look like it was on after about 2 seconds its a cut and glide job. To guard against a failure on climb out dont run the engines at full power for takeoff. 80% is likely to do fine. Then take a long ground roll, get in the air, then a very gentle climb as the speed builds as the more speed you have the easier it is to hold it if the engine fails.

Once up and whizzing about i would always go for the fly it home method, keeping 90% power on the remaining engine and dealing with the rest as required. If you feel at any point its getting away from you the cut and glide option remains.

On downwind/final its a bit like takeoff. Both avenues have an element of risk, but like the takeoff you can cover off a few of them by making sure the engines run well at slow speed, and i tend to use a power on approach to prevent the engines cooling off too much.

If you want to go around, with both engines still running do it very gently. Dont just smash the throttles forward. Slowly wind up to about 50% power and then creep up to 80%. If you dont trust yourself, a servo slow on the radio can help in the heat of the moment. If you only have one engine, dont try and go around. I have done it, but it got the heart rate going thats for sure and i dont recommend it. 

 

Pilot skill is a factor for sure, but i would say that any pilot who is confident and proficient with their rudder will be able to handle it without any problem. It should be possible to fly a basic circuit with rudder and elevator alone on almost any model so if you cant do that its time to practice it as i often see videos of twins with an engine out flying all crooked as the pilot has caught the roll with the ailerons and then left it at that. If he corrected it with rudder instead things would be a great deal easier for him.

The biggest thing that will help though is the cells between the ears. Have a plan in your head to cover eventualities. What will you do if XX happens at XX position, whats the procedure, can you find all the switches on your tx without having to fumble for them? I use this approach with all of my models as its the way i was taught when i did full size gliding. I found that many of the things done in full size flying are quite helpful for model flying and most of it comes down to planning and mind set. Its all about not being caught off guard and knowing what needs to be done.

Edited By Jon Harper - Laser Engines on 17/10/2017 12:46:04

[Denis Watkins]

Taking a lead from you guys, with the excellent advice given, is to have in your locker a low speed flat turn scenario.

Just 5 minutes each flying day, complete circuits, at safe height flying rudder/elevator only, on whatever model you have.

Set the model to a nice cruise cruise speed, and leaving those other stick movements alone, fly circuits with rudder/elevator.

This really gives you the ability to get out of some tricky situations, and helps no end when landing without wings swaying up and down, especially 3m gliders that teach you so much.

[Jon H]

Posted by Denis Watkins on 17/10/2017 14:08:43:

Taking a lead from you guys, with the excellent advice given, is to have in your locker a low speed flat turn scenario.

Just 5 minutes each flying day, complete circuits, at safe height flying rudder/elevator only, on whatever model you have.

Set the model to a nice cruise cruise speed, and leaving those other stick movements alone, fly circuits with rudder/elevator.

This really gives you the ability to get out of some tricky situations, and helps no end when landing without wings swaying up and down, especially 3m gliders that teach you so much.

Yup, this is the sort of idea. Making the turn flat is not of paramount importance, but the idea of controlling the plane with the rudder is and its a really valuable tool.

You do make a good point though Denis which is that different types of model teach you different skills which you can then apply to everything else you fly. The more strings to your bow and all that. Its also ample justification for buying a new model!

[Richard Wills 2]

Well a big box has arrived this afternoon. Off first look, it's looks great. Looks like someone saw sense, and it is matt finish.

First impressions are it is not as big as it sounds from the measurments, Fuse is no bigger than my 60 sized Seafire. Nacelles are fairly tidy, can't imagine a 91 in them, there would be nothing left of the cowling. So the 52's are going in. Expected weight on the box is 13 - 14 lbs, I believe them it is pretty lightly built, so I think the 52's will be more than enough. Retracts look OK, may switch them for a set of electric ones maybe.

looking forward to getting it built, looks like it will go together easily and quickly, and it'll look great when it's done.

[Jon H]

Sounds good Richard. got any snaps or are you too busy rummaging?

[Sabre Flyer]

I like the look and size of this one. I can't find a manual anywhere and I would like to know what they recommend as the electric set up. I will be most grateful if you could let me this and if the lipo/ lipo go in the nacelles or in the fuselage.

Many thanks

[Richard Wills 2]

Manual recommends 35-45 motors, 830kv, 5oa esc's. 4s 3200 batteries and 10x7 props. batteries in the fuse. Motor mounts included in the kit.

 

Jon, been a bit busy, going to start it at the weekend so i'll get some and post them up.

Edited By Richard Wills 2 on 19/10/2017 15:51:45

Edited By Richard Wills 2 on 19/10/2017 15:53:08

[Sabre Flyer]

Thanks Richard, that is very useful info. I look forward to seeing how your build goes.

[Richard Wills 2]

Quick mock up on the table and a few photos album on my profile, going to start putting it together tomorrow.

[Sabre Flyer]

Darn that looks good, Richard. The colours on the nacelles/ nose seem to match well and looks a nice matt finish.

[Richard Wills 2]

It does look even better in the flesh, very happy with the overall look. Paint does match pretty well. It's not perfect, but from a couple of yards away you don't notice. Only thing thats going to be changed is those red spinners. They are a nice shape, so I may try painting them grey. At the end of the day, it is an artf, for me they are instant gratification and it does that very well.

[Jon H]

it looks better than I expected in the photos. They matt finish really helps get rid of that 'toy' appearance so I'm quite impressed. The retracts are 30 years old as a concept but being all metal will probably be more than sufficient so I wouldn't change them unless they play up. In general it looks really tidy and I'm tempted to get one. If my current twin bites the dust or I get bored I think I know where to go

[Ray Charnock]

Hi All

I already have this plane and my engine choice is os 55ax two strokes they went in very easy and are good fit in the cowlings i am using 13x6 master airscrew schimitar props and aliminium spnners check out my video on you tube seagull 80inch mosquito. Ray.

[Ian Moody]

It looks really nice but a bit clean if you know what I mean, it needs some weathering.

Do you think two 52 four strokes will be powerful enough Richard now you have felt the weight?

[Ray Charnock]

Dear Ian.

I have already tried sc 52 four strokes in this plane but i could not find a suitable way to set the throttle control wire as the engine throttle arm is in the centre of the engine.

Regards Ray.

[Denis Watkins]

Some 4 stroke arms are easily spaced further away, but the SC has the slow needle in the centre.

I usually fit a mini servo to the engine mount, or the bulkhead

But the most recent SC, I fitted a flexible cable in tube, like bicycle brakes, and this worked fine

Also online, you will see a bellcrank fitted to the engine mount to transfer movement

[Martin_H]

Going to do mine with two Saito FG11's and Master Airscrew 12 X 8 three blade props.

[Geoff Parkes]

Richard, sorry just picked up your thread, i have a Brian Taylor Mosquito 70 inch span, it is lighter than your plane , but I am all electric and I used a set up put together by George from 4 max, 2 x 50-55 motors, 80 amp speedos,14x6 contra.props, 2x4s x 3750 batteries, the plane needed nose weight and I made the machine gun housing removable and the 2 batteries slid in side by side, the radio is powered by a seperate 2s lipo running through a small regulater, this set up has more than enough power and should hopefully help reduce the one motor out problem, 4max stuff ,is not cheap, but with electrics you get what you pay for, if I was to build another twin I would not think about I/c, all that sludge you have to wipe off the plane, all the starting tackle, and the problematic reliability,no thanks, just turn up put the plane together, put the batteries in and fly,the sound of 2 electric props is just as good as 2 i/c motors, thats if you can hear them above the noise of any one flying i/c

[trebor]

Posted by eflightray on 16/10/2017 14:41:28:

I found this video of the model on youtube, --

Ray.

I love it, shame I couldn't understand what they were saying. I thought he was on a bomb run on those two chaps riding the motorbikes. Can you imagine flying like this off our local roads

[Richard Wills 2]

I have been shopping. I am sure the 52's would have flown this ok, but I have lost my sensible hat, and bought 2 Saito FA-82's for it. Managed to get 11oz tanks in, and going with 14x6 2 blade props. Throttle linkage I have used snakes which run under the engine box and line up pretty well. Fuel proofing to do and then final assembly. not long now.

[Bill Walter]

Gentleman

I live in Florida and I interested in a Seagull 80 inch Mosquito.

I would use HH Bl 50's because I think their is less chance of flying on one motor ( engine) and you can do counter rotating props (No torque issues)

Has any one done one like it or have any suggestions where to buy props ?

Are there any PDF manuals on line ?

Bill W

[cymaz]

Posted by Bill Walter on 07/11/2017 17:33:29:

Gentleman

I live in Florida and I interested in a Seagull 80 inch Mosquito.

I would use HH Bl 50's because I think their is less chance of flying on one motor ( engine) and you can do counter rotating props (No torque issues)

Has any one done one like it or have any suggestions where to buy props ?

Are there any PDF manuals on line ?

Bill W

Send Seagull an email, they should help with the manual..it could take a while for them to reply. I’ve looked on line for the manual but with no luck

[Jon H]

I cant find the manual either. Im sure it will be uploaded at some stage.

Bill, dont get too caught up with counter rotating props. Its not important so if you cant find any dont worry