Getting "too high" for the final approach

[teopereira 25]

I almost always arrive too high for the final approach... I follow the descent path, but almost always have to use speed brakes, sometimes even lower the gears well before my destiny in order to slow down and descend faster. I'm using NavDataPro database.

 

Thanks,

 

Teo Halfen

[DaveCT2003 1,820]

Generally speaking, it depends on which Approach (and the type of Approach) you're flying, but with proper speed management and use of the flaps / gear, you can often make an approach without use of the spoilers. There are certainly approaches and/or circumstances for which a pilot might find it prudent to use the spoilers.

 

In the end, it's really about anticipating what you'll have to do, so staying well ahead of the aircraft will help you out tremendously.  Examples are crossing restrictions and Approach Plates which give you speed and altitudes, knowing that the turn you may have a head of you will help you bleed some speed, etc.  Also, put your gear down about 6 miles out will help as well.

 

All pretty general stuff, but it should help you.

[teopereira 25]

Generally speaking, it depends on which Approach (and the type of Approach) you're flying

Mainly Rio-Sao Paulo air bridge routes.

 

I found an interesting topic on this subject: http://forum.avsim.net/topic/340294-realistic-drag-during-flight/

 

When I fly the Rio-Sao Paulo air bridge in a real 737-800 (as a passenger) I don't see the extensive use of speedbrakes.

[Andrea1 6]

Hi,

(not a criticism here) but if you often arrive "high and fast" there is certainly something wrong in your IFR flying technique...

You know PMDG NGX has to be piloted "like a pro" being very near to the real bird performance so you've to "think ahead" to your plane...

I.e.  if I'm approaching at LIMC rwy 35L and I know that just after NOV at 4000 ft I'll intercept my glideslope problably it's better to put an "hard constrains" in my CDU like 180/4000 at NOV to arrive there stabilized at flaps 5 and at the right attitude, and if I come from RIGON knowing that I have to be at 180/4000 over NOV it's better to introduce another limit at RIGON like 210/6000B to arrive there not too much high and at flaps 1 speed..these constraints are important also to "think ahead" if I see that at 5 miles before RIGON I'm a quite high and not sure to arrive there at 6000B it's better to use speedbrakes or increase approach speed and use FL CHG mode instead of VNAV...

Another advice is not believe in your VNAV like a mantra...VNAV mode is not perfect..also in real life and especially if you have a strong tailwind during descent it could give you a wrong descent path..you as Captain has to actively check your descent path and act if necessary i.e. by using FL CHG instead of VNAV and playing with IAS knob (increasing IAS) , applying speed-brakes etc. until you're sure to be on the right descent path again...(Acting instead to be "magenta-boys" it's one of the main reasons by which pilots are so well-worth paied for)..

Another trick for avoiding overshoot could be an early gear down extension during approach (i.e. at 240 kts) before flaps 15...if it's necessary avoiding to have the day ruinded...

It's also important "to feed" your descent forecast page in your CDU with winds and altitudes if you've strong tailwind during descent (reading them by your wxr engine i.e. if you're bound to LIMC and flying i.e. at FL300 you can read your LIMC wind at different altitudes and insert i.e. FL240, FL120 and 6000 ft wind data...)

Anyway you've to study and improve your flying skills..firstly by starting from the tutorials flights...

Ciao

Andrea B.

[DaveCT2003 1,820]

I typically ignore the "Drag Required" message on the CDU... because I'm not going to wear a dress, wig, and lipstick for ANYONE, regardless of my flight profile!

[Sam 68]

Hahahaha great one Dave!

[Rocky_53 1,566]

The NGX is a very slippery aircraft and requires some good flight planning. I believe if you're aware of this factor then it becomes a lot easier to anticipate things on your approach. I used to get caught out, but now I'm always checking height and distance mentally once I get to within 120 miles of the airport, even further away if I'm flying above FL340. A good yardstick is to equate 3000' for every 10 miles.

[G550flyer 1,010]

I'll make one key note. I myself find that the aircraft is a tad little too slippery. This seems to be a trend with most PMDG aircraft. I'm not bashing PMDG at all. I've seen this type post before and many will quickly point out pilot technique. I have a close friend who flies the BBJ and the C-40C. I discussed this with him shortly after I purchased the NGX. He said the jet descends like any other jet. We both flew KC10s and he said it descends similar. I'm a real world guy and I've flown heavies, mediums and light aircraft. They all tend to descend the same(2000 to 2500fpm at descent speed/1500fpm below 10,000). In all of the aircraft i've flown, you can do 1500fpm clean max at 250kts. Anything more, and she will speed up. When I see new guys dail more than 1500 down in the vert speed, I remind them they will need drag. The DC10 was slippery and I currently fly one of the most slippery jet of them all, the G550. This aircraft is so clean that you have to pull the power at the 100ft agl and only add 2 degrees to the flare or she floats for ever. In every jet I've flown, if you set 1,200 to 1,300fpm at 14,000ft, you will definitely reach 250kts by 10,000ft. We call this technique 13 at 13 or 12 at 12. This is done at idle clean.

 

Now I did a test to show some comparisons. The actual training manual says that below 20,000ft, typically descent rates are as follows. 737-600 to 900. clean and idle=2200 at 280 and 1700 at 250. During my test with the -800, at 280 i got 1900 vs 2200 below 20,000ft. At 10,000ft, I had 1200fpm vs 1700. That's less than the 1500fpm I see in my real world slippery jets. The training manual falls in line with the information from my friend.

 

May not seem like a big difference, but 300 to 500fpm is a factor over a period of time. In the real world, as long as you use 3 to 4 times the altitude to loose for descent distance, you have plenty of time to slow. The training manual recommends 3 but I use 4 in the Gulfstream. Though I don't recommend it, I added drag to the NGX speed brakes and ride them in. In the Gulfstream, I only use speed brakes when held up by ATC. If i can get a G550 into aspen, you should be able to easily manage a normal descent in the 737.

 

Again, not a bash on PMDG, just what I observe compared to my real world experience and aircraft.

[Andrea1 6]

Hi,

I can't agree...

I've been in a fixed base B738 trainer ..it's slippery like ngx...ngx is realistic..during descents..

Jets are not all the same during descent like you say (there is a difference also between a winglet or a not winglet version of the B737 i.e.), aerodynamics is different..cross area, wing drag to lift parabolic curve is differents, wing area and wing area to a/c weight ratio is different.. engine cross area etc etc..

How can you say that jets are all equals?

how can you compare different aircrafts?

Best

Andrea B.

[G550flyer 1,010]

Hi,

I can't agree...

I've been in a fixed base B738 trainer ..it's slippery like ngx...ngx is realistic..during descents..

Jets are not all the same during descent like you say (there is a difference also between a winglet or a not winglet version of the B737 i.e.), aerodynamics is different..cross area, wing drag to lift parabolic curve is differents, wing area and wing area to a/c weight ratio is different.. engine cross area etc etc..

How can you say that jets are all equals?

how can you compare different aircrafts?

Best

Andrea B.

I think you may want to read what I actually posted. I said they are similar and tend to descend the same. I didn't say they are equal. But, maybe you are an expert. I was going off of my real world pilot experience. For example, the actual 737 manual says that typical descent rates at 250 is 1700. The DC10 and the G5/550 is 1500ish. 1500 and 1700 are similar don't you think? Now, lets actually compare some different jets and let you be the judge. I'm big into aircraft performance and that's my thing. In the AirForce and in my current outfit I am the aircraft performance guru. Even as a flight examiner,alot of my questions are about aircraft performance. I believe in precision flying that's all. I am a performance manual collector and I have a C-9B, 757 and DC10 manual lying around. Lets compare some numbers here.

 

DC-9-30(flight performance manual)=at 110K(110,000) Descending at 280kts is 2200fpm clean from the charts. At 250kts, it's 1500fpm. At 80K, at 250kts its 1700fpm. Similar to the 737NG. See where im going with this?

DC10-30(PM/experience 4500hrs)=descending at 320kts 2000 below 20,000 and 2200fpm above 20,000ft. At 250 at max landing weight (436K) 1500fpm max.

757-200(FCTM)=typical below 20,000ft descending at 290kts 1800fpm and at 250kts 1500fpm.

777(FCTM)=typical below 20,000ft descending at 310kts 2200fpm and at 250kts 1400fpm.

G5/550(PM/experience 2000hrs) below 20,000ft descending at 300kts 2200 and 250kts 1500fpm at typical landing weights.

737-700(FCTM)=typical below 20,000ft descending at 280kts 2200fpm and at 250kts 1700fpm.

 

Yes Andrea, I actually compared some very different jets. Here's the interesting thing, I said they descend 2000 to 2500fpm. Based on the jets I compared, they are in that range with the exception of the 757 which is only 200ft outside that range but close. I said 1500fpm below at 250kts, again spot on or very close. Again this is based on my real world experience. I was amazed by it as I moved from jet to jet. You even hear these descent rates when different guys are questioned by ATC.They all recommend 3 times the altitude to descend for planning. This tells me they are similar as I stated based on their own speed schedule. The 757 actually recommended 3.5 times the altitude to descend. The DC10-30 is very close to the 757. We get higher descent rates due to the higher descent speed of 320 compared to 290 in the 757. I learned to use 4 times the altitude in the DC10 because 3 was just too tight. Get behind in the descent in the 10 and you will never catch up unless you request a 360 or drop gear way earlier than normal.

 

As far as your question about the different aerodynamics and all, I don't know. I don't design them, I only fly them. If you question the charts or numbers I posted, inbox me. Facts are facts. PMDG also provided charts so you can verify the 737 numbers.

[thepilot 565]

My piece of advice in this regard:

 

-enter the destination airport identifier (can also be the ILS/DME one) on the FIX page, then draw the 30 mile circle (enter "/30" below). Plan to be at FL100/10000´ when passing it. This tip comes from an actual Boeing 737 Captain, Mike Ray.

 

-Set flaps 5 before intercepting the glide slope and adjust the speed accordingly. Depending on the weight this shouldn't be more than 180 KIAS. I have found it tremendously hard to reduce speed when descending on the G/S already with a rate between -800 and -1000 fpm while I am still doing ~200 KIAS with flaps up or F1.

[WfordJr 1]

 

 

-enter the destination airport identifier (can also be the ILS/DME one) on the FIX page, then draw the 30 mile circle (enter "/30" below). Plan to be at FL100/10000´ when passing it. This tip comes from an actual Boeing 737 Captain, Mike Ray.

 

Works great. Been doing that for years. Also set another fix at runway identifier, inverse course and 10mi to intercept ILS. 1500ft AGL of airport altitude. Cant go wrong

[Guest]

Hi guys.

 

I can confirm the 737-800 is a VERY slippery aircraft and also the PMDG NGX is VERY similar to the real aircraft.

 

The key is anticipation and energy management, in reality you can be on profile at 10,000ft and ATC all of a sudden give you a 10nm short cut and you're all of a sudden 3000ft high.

 

If you're high on profile things you can consider...

 

Above FL100

 

• increase IAS (up to 330kts) and speedbrake for additional drag

 

Below FL100 based on MLW

 

• 250kts Clean = 1500fpm ROD (250/nm)
• 250kts Speedbrake = 1800fpm ROD

The best height loss per nm during configuration for approach

 

• 220kts/F5/Speedbrake = 2300fpp ROD
• 180kts/F10/Speedbrake = 1500fpm ROD

If still high on profile in reality you would ask for extended vectors or holding which may be your only option to avoid a High Energy Approach.

 

A very good rule of thumb is the 3,2,1 rule

 

3000ft, 200kts, 10nm (from touchdown)

 

and always remember, always fly an approach to go-around. A landing is always a bonus!

 

 

Samuel Breese.

[G550flyer 1,010]

 

 

250kts Clean = 1500fpm ROD (250/nm)

Keep in mind, I never said the NGX is unrealistic. I only stated that the NGX is a tad bit too slippery. Tad/Bit meaning very small amount too slippery. Training manual said 1700 and you said 1500 clean. In the NGX I get 1200 below 10,000 clean in the -800. My whole post was to say it's a tad bit on the low side compared to the training manual. Even when compared to your number.

Good day Gents.

[teopereira 25]

Thank you all for the advices, I'm inserting the winds now in the descent page and choosing the lowest and slowest for the legs, plus lowering flaps earlier, so things are getting better...

Btw, your posts were very interesting, being pilots of different aircrafts and reporting your impressions about them!

 

Thanks!