Steeper descent profile

[NeilC 3]

Hi Guys,

I am fairly new to the DC-6 (having cut my teeth on the MD-83 for the past 15 years).

I am quite familiar with constant speed props, but am really struggling to get the DC6 to descend.  I have read that you need to plan well ahead and start descent early, but I am having real problems slowing down.  When using the AFE, having completed the inrange checks, you need to slow down far enough to be able to drop the flaps as part of the final check.  I have also read elsewhere that you shouldn't go below a BMEP of 80 (and of course you should avoid the props driving the engine at all times), but at the lowest possible settings in level flight, the speed bleeds off so slowly.

Most of my flying is around the mountains of Austria and Switzerland and I am finding it impossible to fly certain approaches, as I just can't lose the height necessary.  I know that the DC6 wasn't built with steep approaches in mind, but they have operated into airports such as LOWI, so it must be possible.

Also, on final (inside the inner marker 4/DME) is it permissible to go below 80 BMEP?

Sorry for all these questions, I am loving the DC6, and would like to do it right.

Neil 

[downscc 1,327]

6 hours ago, NeilC said:

Hi Guys,

I am fairly new to the DC-6 (having cut my teeth on the MD-83 for the past 15 years).

I am quite familiar with constant speed props, but am really struggling to get the DC6 to descend.  I have read that you need to plan well ahead and start descent early, but I am having real problems slowing down.  When using the AFE, having completed the inrange checks, you need to slow down far enough to be able to drop the flaps as part of the final check.  I have also read elsewhere that you shouldn't go below a BMEP of 80 (and of course you should avoid the props driving the engine at all times), but at the lowest possible settings in level flight, the speed bleeds off so slowly.

Most of my flying is around the mountains of Austria and Switzerland and I am finding it impossible to fly certain approaches, as I just can't lose the height necessary.  I know that the DC6 wasn't built with steep approaches in mind, but they have operated into airports such as LOWI, so it must be possible.

Also, on final (inside the inner marker 4/DME) is it permissible to go below 80 BMEP?

Sorry for all these questions, I am loving the DC6, and would like to do it right.

Neil 

Hi Neil, please note that PMDG asks that we use our full name on all posts in their forums.

You are correct, the descent requires planning.  I usually descent using the MP gauge (in my opinion any positive BMEP means the props are not driving the engine, not sure where 80 comes from).  I plan for a 500 fpm descent at about the same or slightly higher speed that I am cruising.  This is achieved by reducing power to 25 inHg, and leaving the props alone or increasing to 2200 RPM.  The key piece of information is distance required, and that depends a lot on your ground speed.  If you have DME or GPS use it to get a cruise groundspeed and use that for the descent planning.... true the groundspeed will decrease for a give airspeed as you descend the your airspeed is likely to increase thus offsetting the decrease.  We just want to be close, exact is not necessary.  So 240 kt GS is (240/60) about 4 nm/min and a descent of 500 ft/min means every 1000 ft of descent will require about 8 nm.  If you are at 8000 and want to descend to 2000 you need to start down at least (6 x 8 ) 42 nm before airport and maybe a little more for a straight in approach.  The secret to speed control is to level off at the 2000 ft AGL point and bleed speed there, you only need to bleed off enough to start the flap sequence... once there are flaps out you get dirty and slow down easily.  Alternatively, you can slow down before you go down, this method works great if you need to shorten the distance for the descent.

A steep approach is exactly what you get will full flaps, I normally do not put out that last notch of flap until I am over the fence or approach lights.  Yes, during approach you can reduce BMEP to any positive number.  Unless you were too fast, those barn door flaps are going to need some power on to keep from falling out of the sky anyway.

Try flying without the AFE.  I only used that feature once during beta testing.... I understand it's usefulness and utility but there really isn't a need for it in a simulator in my opinion.  Doing the work yourself will build your confidence in being able to handle this beautiful machine.

[NeilC 3]

Thanks for the reply.

I do put the AFE into hold and set the props/engines myself a lot of the time.  I am just struggling with losing height quickly.  I suppose if I need to descend into a valley from above mountain peak altitude, I need to configure to full flaps and then descend.  To do this I need to reduce the engines down manually to lose the speed, but had read that a BMEP bellow 80 was not used in the real world.  Flying variable pitch I normally stick to the rule that the manifold pressure is above the prop speed it should be ok.

Thanks again,

Neil

[downscc 1,327]

2 hours ago, NeilC said:

Thanks for the reply.

I do put the AFE into hold and set the props/engines myself a lot of the time.  I am just struggling with losing height quickly.  I suppose if I need to descend into a valley from above mountain peak altitude, I need to configure to full flaps and then descend.  To do this I need to reduce the engines down manually to lose the speed, but had read that a BMEP bellow 80 was not used in the real world.  Flying variable pitch I normally stick to the rule that the manifold pressure is above the prop speed it should be ok.

Thanks again,

Neil

I think you are on the right track as far as your logic goes.  I'm not sure about the BMEP >80 being a thing, maybe just a suggestion but by definition any positive BMEP number means the prop is not turning the engines.  I do try to keep the MP at 25 inHg in a normal descent, and any lower than 22 inHg (I think) you get a gear horn so there are practical limits.  The shock cooling concern for these engines isn't a normal concern but one does avoid a rapid cool down.  The descend into a valley is best done using the adage "go slow or go down."  In other words you cannot do both, only one or the other so you might want to reduce speed to 190 drop 10 deg of flaps and descent at 2200/25.  If you are going into a well you could drop gear.  Watch your CHTs and do the slow down at altitude in 2 inHg steps of MP slowly decreasing to decrease CHT on a ramp rather than a step.  Other than descending into a valley (I've done this at Lake Tahoe CA) this procedure is not a "normal" procedure.

Edited August 1, 2018 by downscc

[TheFinn88 13]

Hi!

I also had some troubles, but I've found some tricks to fly into airports around central europe:

1. Look out for alternative STARs, maybe search for a route around your destination and approach it from the other side where you maybe won't need steep angles.

2. Decrease your airspeed/power before you start your descent, this will prevent an IAS of 200+ KIAS, so that you just need about 10nm of level flight to slow down to the magical 174 KIAS to lower gears/flaps.

3. If required, I slow down to 170 KIAS and drop the gear before starting the desent. The DC-7 actually had an "airbrake" lever, which dropped the main landing gears to achieve steeper descend angles (apparently they learned something from the DC-6).

4. If you see that you won't make the required altitude and speed in time, ask ATC for a hold before the FAF. It's easier and much less annoying to fly some holding patterns for descending and slowing down than to make a go-around or even crash the plane by forcing it onto the ground.

Edited August 6, 2018 by TheFinn88

[TheFinn88 13]

A little addendum to my post after my yesterdays flight into KMDW. The MOTIF6 STAR requires to cross MOTIF at 10'000ft and the next waypoint MINOK at 6'000ft, with just 15.6 nautical miles between them. For this STAR I slowed down to 170 KIAS and dropped my flaps to 10° before starting the descend from 13'000ft to 10'000ft between the BDF VOR and MOTIF. Just right before MOTIF I reduced my airspeed to 160 KIAS and dropped my flaps to 20°. In this configuration I was able to achieve a descend rate of about 800 feet per minute while keeping 160 KIAS.

With an airspeed of 160 knots you need about 5.8 minutes to cover these 15.6 nautical miles, while you have to descend 4000 feet. At a rate of 800 feet per minute, you'll require 5 minutes to descend from 10'000ft to 6000ft. So this can be done, but only with a good descend planning and some drag extended. When you would try to fly the MOTIF6 arrival in clean configuration, you won't be able to comply with the altitude restirctions. With an airspeed of about 180 KIAS at 0° flaps and a descend rate of about 500 feet per minute, you would require 8 minutes to descend from 10'000ft to 6'000ft while you would reach MINOK after just 5.2 minutes.

Maybe with additional drag by also extending the landing gear, you are able to achieve an even greater rate of descend. I havn't tried this yet. Also I was quite light at a gross-weight of just 73'000 lbs. Don't know how the six would perform heavily loaded.  And in a controlled airspace (I always fly on IVAO), the ATC probably would vector you on a different route to get you out of the way for faster planes.

[downscc 1,327]

9 hours ago, TheFinn88 said:

The MOTIF6 STAR

It is highly unlikely ATC would give this arrival in a clearance to a DC6.  This aircraft can be flown above the TA (18000) but if you look at the performance charts you might notice that there is no reason to do so.  I recommend that flights be planned with cruise altitudes between 8500 -17500 and go VFR if weather and terrain permitting.  You will find a few terminal procedures for low and slow at places like LAX, DFW or IAH and surrounding airports, but if the procedure is for turbojets or turboprops then you need to assume its not for the DC6.  Besides, it's a lot more fun to fly VFR in this beautiful aircraft.

[TheFinn88 13]

I was cruising at 15'000ft, so it was in the range what you call a normal cruising altitude. And turboprops flying the CVA.MOTIF 6 arrival at KMDW are expected to cross DIPSY (the first altitude restriction on this route) at 13'000ft (jets at 15'000ft). So I don't see any troubles in flying that STAR with the DC-6 too. Sure ATC might have vectored me on a different route (as I've already written in my earlier post), but there was none online, in such a case I stick to a STAR that the DC-6 is able to comply with. There are loads of STAR's that have altitude restrictions above 20'000ft (e.g. the ENDEE 4 arrival at KMDW that starts at FL240 up to FL330), some airports have alternative STARs with lower altitide restrictions, and some airports don't. In such a case I take a look at the approach charts and search for the IAFs. Some of them have a VOR near to them (or the VOR might even be the IAF), and I'll pick that as my last waypoint of my route. But if there is a STAR like the CVA.MOTIF 6, I at least try to fly it.

Flying VFR is fine, but I would like to see you flying the VFR approach routes for LSZH with the DC-6, which are solely meant for small aircraft!  Even if you could comply with them, your PAX would be screaming in the back.  I always wondered how big aircraft fly VFR in and out of a controlled airport? Lets take LSZH again, it has published visual approach routes and waypoints, but they are really only meant for small single or twin engine piston aircraft (and maybe the JU-52), and it has pretty small holding patterns (with a speed restriction of 90 knots) and quite sharp turns which in my opinion the DC-6 can't handle because she's flying much faster. But the Red Bull DC-6 has already been many times at LSZH, and I suppose that they flew VFR. But how is it handled? Are they vectored by ATC in and out of the CTR when they can't stick to the visual departure and arrival routes? Or do they get special clearances, e.g. to fly direct to the visual departure waypoint by ignoring the published routes?

This is one reason why I mostly fly IFR, because I really don't know how a DC-6 is flown VFR in todays controlled airspace as most of the published routes are meant for small aircraft only. And the other reason is because I'm flying in real time and on evenings, it's mostly getting night before I get to my destination (especially during the winter)... And Switzerland doesn't permit night VFR flights (only on some occasions during the summer).

[downscc 1,327]

8 hours ago, TheFinn88 said:

But the Red Bull DC-6 has already been many times at LSZH, and I suppose that they flew VFR. But how is it handled? Are they vectored by ATC in and out of the CTR when they can't stick to the visual departure and arrival routes? Or do they get special clearances, e.g. to fly direct to the visual departure waypoint by ignoring the published routes?

One of the PMDG DC6 technical team members is a pilot on the Red Bull aircraft so maybe he will chime in if he's lurking.  I'm not familiar with European flight operations but I'm not surprised there is very little VFR in an area so small with so much traffic and highly regulated.  My VFR comments were following your post regarding a MDW arrival, where you will find substantial VFR traffic within the confines of the Class B airspace.   Back to Europe: I am certain that the DC6 is not going to be treated the same as a turboprop commuter, and that flight safety will be ensured so I'd say yes to a combination of vectors and clearances that are suitable for this aircraft.  The main point is that you cannot shoe horn this airplane into a set of terminal procedures created for modern aircraft.

[BlueStar 323]

On ‎8‎/‎9‎/‎2018 at 1:45 AM, TheFinn88 said:

 And in a controlled airspace (I always fly on IVAO), the ATC probably would vector you on a different route to get you out of the way for faster planes.

In the real world if I couldn't make a speed or crossing restriction, I've told ATC and they have always worked with me.  Where the problem comes is not telling ATC.  🙂

All the crossing and speed restrictions that are on SIDS/STARS/HOLDING are to make ATC's life easier and can be changed by ATC if and when necessary.

[metzgergva 28]

I can only talk about my RW flights on the DC-3, which has a similar descent profile. They key is in the diagram on an approach and you will see there that you slow down in the pattern early and use flaps and gear to accomodadate to descending. You can basically fly any VFR pattern used for larger GA aircraft like a Piper Chieftain.

Here is an extract from my DC-6 Flying Guide:

A good pattern speed with 20° flaps configuration would typically be 125 kts (Vref+35) for downwind and 105 kts (Vref+15) for base leg which you get by setting flaps to 30°. The engine settings are then similar to what you used during a shallow descent making it easy not to change engine setting too much. Best practice is in fact to keep the engines in a small window around 30 in for level flight down to 25 in during a descent with RPM at 2000. When you turn on final you drop the gear and increase RPM to 2300 1/min. Again vary MAP between 28 in for flaps 20° and 30 to 32 in for flaps 40 to 50° for matching final approach speed. Therefore, speed management during approach and landing should be managed by adding drag from lowering flaps and gear and not changing engine setting beyond those small adjustments.

Now when approaching larger airports like Zürich or Geneva in the DC-3, we use the VFR entry points or may get radar vectors to be established on the approach 3 miles out so that we can fly a 3° descent with 500 ft/min at 100 kts. We always need to remind the tower that we have an 80 kts final speed and that they need to keep enough space behind us. Also that they can alow aircrafts departing longer as we come in sooo slow. In the beginning of the DC-3 times in GVA , I have see two go arounds behind us and 5 planes at the holding points. Now all tower ATC know us well.

Not much difference for the Connie or the DC-6. Everything just 15 kts faster.

Now for the steep approach into Innsbruck via RTT and the LOC DME 08/26 EAST, you can only fly those 3.77° angle descent  with flaps 40° and gear down.

I have not come across an 80 BMP minimum. The important rule is to have MP equal or slightly above RPM/100. 

As for DC-3 or Connie descnt planning we are using only 300 ft/min, so you need to start out early from your destination.

[NeilC 3]

Thanks, 

This is really great info.  I was flying around this morning in Manfred Jahn's fantastic DC3, and came in a bit hot and high, and just could not lose the speed enough to get below 100kts and drop 1/2 flaps.  I was running 1700rpm and 17 MP, and it still would not bleed off (I ended up doing an orbit on 3 mile final (something which VLM F50s used to do at the airport where I control - EGLC - but was then outlawed by the CAA).

At what stage is it acceptable to reduce MP below RPM?  Only as you flare, or on final as well?

I am obviously treating the DC3/6 too much like a modern GA twin.

Thanks again for the info.

Neil

[downscc 1,327]

6 hours ago, NeilC said:

At what stage is it acceptable to reduce MP below RPM?  Only as you flare, or on final as well?

Once the gear are down you should not need to reduce power by that much, the drag from flaps and gear will normally require a reasonable power setting.  If you are steep (3.77 is steep but I've flown 6 deg into Aspin) you need to get all the barn doors open (Flaps 40) and just keep a positive BMEP... you should need some power to keep from sinking like a rock.  Don't worry about MP at this stage, the positive BMEP assures you are not windmilling.

[NeilC 3]

What about the DC-3. No BMEP gauges, so should/must you always keep MP above RPM, even on final if trying to slow (I appreciate that it is probably bad planning leading to all of this, but is it allowed?)

[downscc 1,327]

2 hours ago, NeilC said:

What about the DC-3. No BMEP gauges, so should/must you always keep MP above RPM, even on final if trying to slow (I appreciate that it is probably bad planning leading to all of this, but is it allowed?)

Keep it simple... the whole issue is because there is a reduction gear and it's designed to apply thrust.  You get into trouble when the propeller drives the engine which creates negative torque.  As long as you don't "windmill" the engine you are good.

On more modern light GA twins, other than the geared C-421 and other similar geared engines, the power during descent is to prevent cooling the heads too quickly.  This is not an issue with these large radials.